Oh, I am so sorry you feel this way.
Believe me, your daughter loves you...but she obviously loves her grandma, too, and there's nothing wrong with that.
But maybe is your M. spending more time with her than you are? Or, when you are spending time with your daughter, you are busy doing things that have to be done (cleaning, cooking, laundry, etc) where your mom just gets to hold, cuddle, and play?
Try to make every effort to spend the time with your daughter...and if you are busy (we all are) then just try to include her in your chores and make her feel very important.
If they are sleeping together, do you live together? Then it really makes a lot of sense that your M. is an important part of her life. You are, too! Just try to do your best!