C.C.
Hi Page,
I feel for you. While I am very close with my mom, my dad has always had a very strained relationship with his mother. She was not a good mother when he was young (nor was she a good grandmother to me) - too much to go into here, but suffice it to say that her behavior was negligent at best and abusive at worst.
So, now that Grandma is 85 and has nobody left in the world who likes her, people are always asking my dad, "But one day she will be gone, and won't you feel bad that you didn't spend time with her?" He has made the decision that he does not want to see her, period. This has meant that he has missed a few big family events - his nephew's wedding, niece's baptism, etc. But, he is happier for it.
Don't feel guilty or anxious for your feelings. It is hard when people who were supposed to love you unconditionally, didn't, or people who were supposed to support you into adulthood, left you hanging. You may never truly get over those feelings. Just because she's your mother doesn't mean that you are obliged to overlook all of her previous behavior or forgive it, unless that is what serves you best. And it doesn't mean you are obliged to play hostess either.
If conversation is uncomfortable, you can suggest events where you do not have to really talk to her (such as going to see a movie, or going to a ball game or concert). Or if you are comfortable with the idea, you could ask her if she would like to babysit for your kids (if they are of the age where they need it) while you and your husband go out for dinner, so she has time to see the grandkids alone. Generally when I am in a situation when I have to deal with Grandma Awful, I try to bring a lot of pictures, scrapbooks, etc and ask to see her photos from when my dad was little. I have found that I can deal with her on that level (and that level only, pretty much), and once we have run out of cute little stories about our kids, I pack up the kids and leave!
Good luck, I'll be thinking of you and wishing you strength!