I think you need to set some ground rules with her because it's pretty clear that you both have very different ideas and attitudes to parenting and once your DD gets older, she is going to be able to pick up on that and realise that you do things differently. If your mother lives with you in your house then she needs to keep her mouth firmly closed and leave the parenting up to you - even little comments will be enough to undermine your parenting and send mixed messages to your DD. I would talk to her about it and let her know in no uncertain terms that you would greatly appreciate it if she stopped using those comments.