Welcome BellasMomMom,
This is a wonderful site and cyberfamily to really have as a sounding board also. It may be very good for you.
I'm sorry to here about all your health issues....you're quite young to be suffering from all of these afflictions. I hope that you are taking care of yourself in a top notch way.
I'm so sorry to hear of the loss of your mom. That is a huge sorrow for you. I hope your heart will accept this in time. Know that a part of your mom will live on in you and your family.
I might be the bad guy here, but I'm going to be very honest with my take. I can tell you're stressed to the max as I felt the stress just reading the post. You seem like a very loving mother and grandmother. Your are also grieving the loss of your mom which might cause us to "overfocus" on the others left in our lives. However, IMO you might want to pull back a whole lot. It seems that your best intentions are making your YD and her boyfriend to feel very overwhelmed. I can see from the outside looking in how that could happen here. GD is
their child and if they want to do the "firsts" with her most of the time, I get that. Even if you don't care for the boyfriend (oh have I been there), it's still your YD's choice to make. I don't think you should have to walk on eggshells and of course we shouldn't have to check with every single "first", but I can see that the newer parents want that joy for themselves with certain things and rightly so. I'm sure you were blessed with doing those "firsts" with your children. Sometimes being a newer grandma feels like our GC are more like our children....but they are
not. Try very hard to remember that. (I have had to do that as well.) You sound way too involved (as I was). I am still growing through this transition every day as we all are.
I do not blame your YD for not wanting her child to be around your OD much as you said yourself you feel she has the issues of being bipolar as well as drug abuse. A good mom wouldn't really want her child to be around that in much more than a small dose if your OD is not getting the proper meds she needs for herself and is not in recovery for the drugs.
Sometimes our loving actions are just too much for our AC. Many of us have been there and done that with bad results. We have to let our AC go....they are not babies anymore and to get that through our heads is a tough reality we have to face. To act otherwise (i.e. reminding your YD of with a laundry list of all the things you did for her over the years) is more like a guilt trip to her that doesn't really help in the long run and is only counterproductive than what we are trying to achieve. Your YD is growing in her own independence and trying to make her feel guilty for your benefit or to attempt to make her "see" things your way is going to backfire.
As far as being an hour late with the GD without a phone call by you only creates undue worry for the parents. To those waiting it may feel that your not calling and thinking everything is fine is an assumption on your part that they having nothing to do except wait for you. IMO, a phone call would have been the proper thing to do, plain and simple. If someone is late with our own babes, we want at least the courtesy of the call. Nothing is "just fine" to the parents when someone is so late returning their prized possession that is there child.
I'm a recovering champion enabler myself (hence your OD still living there, being disrespectful to you in your own home and taking drugs). Enabling helps no one and hinders her own growth to face the reality of life and causes resentment and stress for us. We will not always be here on the planet to save them. Just a little food for thought. If OD truly has a dual diagnoses of "bi-polar" and "drug addiction", she needs more help than what you are able to offer. I have a DD who has a dual diagnosis of major depression, anxiety, and drug addiction currently in recovery. Your OD needs to be ready to admit there's a problem and then get help. My DD said to me she wanted the help but didn't know where to go or what to do, so I did guide her in the right direction for that and gave her a ride there (my donation of "help"). To enable this AC makes us just as "sick" or "sicker" than they are. The help I was able to give my DD was to take her to the hospital and then to rehab. The rest is up to her. Period. We are not responsible for the poor choices they made with the drug addiction. I have to be intentional about not enabling and sometimes I slip in small ways, but the regular "party" that was going on all at my expense is over.
If you want the relationship with your YD to be repaired, you may need to pull way back and let them do the contacting if they want you to watch the GD. A possiblity might be for you to let them know to let you know if they would like you to as GD is always welcome, maybe just "ask" for GD once in a while but not like it is now. But from the outside looking in, you may seem quite overbearing to them. Try to focus on backing off some. Fill your time and thoughts with good things for yourself. It will help you get through the transition of this change and you deserve it after all ! Try it, you'll like pampering yourself.
I hope you will be able to keep posting and we all try to give our honest humbling opinion here, but they are just that: opinions.
Warmest thoughts to you BellasMomMom, as you journey through this new phase in your life of "letting go" and letting your AC be them. It really helps to focus on ourselves as people besides moms and it is truly a new and growing journey. (and less stressful I might add!!!) Please try to take better care of yourself because you need a healthy mind and body as possible. You can be a wonderful example for your AC and your GD by doing so. And in time, you will get to see your AC watch their own babes grow away as they gain their independence and you can stand in the shadows nodding and wondering "how does
that feel!?"

Enjoy your GD when you can, but just focus on your personal needs for a change. I assure you it will get easier with time to do that and you may find you will get more respect from those around you when you do. Please take care of your body as best you can so you can be there for the GD during those visits you do have with her, but more importantly, for yourself.