I think the situation could be much worse - just turn the tables and ask how you'd feel if she wouldnt buy anything, wouldn't be there for you, wouldn't want the best for the child, wouldn't be so excited about her grandchild... then I think you'd have something to complain about.

As it is, she's just expressing her love and excitement and although this may annoy you, perhaps just grin and bear it as much as you can. She will be a wonderful help to you and will be there when you need it not to long from now.

Good luck. xx