Sometimes I think mums can do too much and then all the help given is seen as a "right". I have seen this with a friend of mine whose daughter, I think, really took advantage. In the long run, it didn't help her daughter as she became too reliant on my friend to look after the baby, change and feed him, do all the cooking, etc. etc.
When my friend had to attend to a family emergency and was unavailable for a few weeks, miraculously her daughter managed to do all the things she had previously been unable to cope with.
I think it would be a bit drastic to suddenly withdraw your support entirely, as your daughter has got used to your help and may feel overwhelmed. That, in turn, may leave her tired and irritable, which could affect her relationship with the baby. It's good to give a helping hand now and then, but not too much as you will end up exhausted and very resentful - not good for either you or your daughter.
I hope things soon settle down.