WWYD? (MIL related)

TinaL99

We had a great dinner with the ILs yesterday.  MIL and I were in the kitchen while Stella was playing with her new pink Cadillac (a garage sale find!).  MIL turns to me with tears in her eyes and tells me that she thinks of me as her own daughter (DH is an only child) and hopes that I will start calling her Mom. 

I LOVE my MIL and you guys know that we have a great relationship with her and I've felt like more than just her daighter-in-law for a long time.  I do not feel comfortable calling her Mom.  I just don't.  I have a Mom and besides the fact that I think it would make her feel uncomfortable and possibly jealous, it just doesn't seem "right" calling my MIL Mom.  I hear one of my friends call her MIL Mom and I cringe a little bit.  I'm not doing a very good job of explaining myself, but I don't have the heart to tell her that I don't want to refer to her as Mom. 

WWYD?  Call her Mom once in a while to apease her?  She is the nicest, sweetest person in the world who does so much for us.  Part of me thinks I should just suck it up and do it, but it will take A LOT of getting used to.