What should I do?

so my boyfriends mom has been offered to watch our 2.5 year old. she never does or will say she is off and can do it but never follows through. At my son’s baptism she said how my daughter should spend the night with her they’d have so much fun. she is known for a drinking problem. she also is moving around alot from not living with her bf to living with her bf. what would you do?