I have some very mixed feelings about this situation. As a DIL, my parents and DH's parents met for the first time at our wedding, even though everyone lived locally. These two sets of parents had zero interest in each other's lives, and I never questioned it. We all got together for another occasion, and I think they were cordial and polite but mainly disinterested.
On the other hand, when my FDIL's family was visiting when the relationship between DS and FDIL's was becoming serious but they were not yet engaged, I was delighted to meet FDIL's family on that visit. In fact, I would have felt hurt if I had not had the chance to meet and speak with them. We hit it off well, and it was a warm beginning, I thought. For me, it was a wonderful time in anticipation of an extended family, with my beloved DS marrying the dear FDIL.
So your FMIL's desire to meet your parents on their visit seems reasonable to me, and I understand her disappointment. I can also understand your parents' disinterest, especially if you had some negative things to say about FMIL.
In my situation, little did I know that the pinnacle of our shared joy and closeness would be DS/DIL's wedding. It took quite a while for me to understand that DIL had no interest in having a relationship with me (in fact, she is hostile towards me), and that I would no longer be included in any of the many events with her side of the family. With my DS caught in the middle, I became "collateral damage"--that is, I no longer have a relationship with DS/DIL. (It is an irony to see in hindsight that although FDIL's mom on that early visit did not approve of FDIL marrying my DS, I am now the one who is "out" and DIL's mom is the favored one.)
IssaQueen, I would encourage you to have some premarital counselling so you can discuss how to deal with your and FH's expectations of relationships with future in-laws. If you and FH are not clear and in agreement, you may continue to have problems in how you relate to FMIL. Perhaps FMIL will come around when she realizes it's in her best interests to do so. (Or FMIL is insecure and doesn't have the social skills to deal with it better?) Of course, I would be guarded in the meantime.