This sounds like the note you should send. It is sincere and thoughtfull!!!!!!

I would take an opportune moment when we were alone and give her a hug and tell her how much it meant to you that she shared the quilt with her friends. That you are so happy that she is your MIL because she raised such a wonderful son and (insert several things here) . I'm sure you can find a few things about her to really seriously praise.
I then would tell her how glad you are that she is your MIL. You have acquaintances that relate horrible MIL incidents to you and that you are always so happy that she is not like that.
You get way farther with honey than with vinegar!! grin

How old is she? Could it be an aging problem?

My MIL didn't like me either. She was a little thing(5') I'm tall. I helped her get in my car the front seat, and put the seat belt on her. When driving down the road she said "You don't like me very much." I asked her why she thought that. It was because nobody ever let her sit in the fornt seat anymore because they thought the seat belt would kill her. Then we went to eat. She ordered at the counter in this real low voice, and when I ordered she says in the loudest voice you ever heard. I suppose I have to pay for it all." I did make her 2 quilts, and would you believe she told everybody I was her favorite DIL. There were 3 of us DIL. It will work out in the end. She passed away at 98,but she still knew who I was, the one that made her the great quilts.

I second this

That was my first thought too. ...but how do you know that she thinks you don't like her?

Call your MIL......."just to say hello" and add
"I love you, Mom" before you hang up. That'll do it.

I like mommamac's suggestion too. Good luck with your feelings.

An awesome way to respond.

Maybe send/give her a card that says how much you care - maybe it's less "intimidating" than saying it in person. Not sure if this is good advice or not - I always communicate how I feel - don't like people "wondering" about things so I try to be clear. Good luck!