I feel for you Milly.My DD lives close and when expecting her first baby announced they would use a child minder or nursery on return to work ,and wanted me to be a grandma that babysat because I wanted to .Then she started a new job with a longer commute,and her parnter changed jobs and had lots of overtime.It all got too much for both of us.I was doing two very early starts a week and having the baby at least one night a week,plus extras .I got shattered.She got grumpy and at times very rude and offhand with me.I really was very diplomatic about things that have changed like baby led weaning etc.But the slightest comment seemed to cause offence.I know she was struggling,online a lot for advice and feeling inadequate at times.Plus there were tensions with her partner that thankfully seem to be settling down.
Eventually she reduced her hours and we had a frank discussion - after an argument - and I have withdrawn some of the help.And made it clear,as she is pregnant again,that I'm happy to help but don't want to feel I'm treading on eggshells all the time. I react less if she is abrupt and just walk away calmly - which seems more effective.It really can be very hurtful.As they say you love your children- but don't always like them !
I hope you can find a way to help your DD appreciate and respect the help you are giving.And please put yourself first for a while.You're no help to her if you get so rundown ,and she needs to learn to cope .We all had to.That doesn't mean not being there if she is ill or an emergency happens.But if it's general childcare let her work it out for herself more.
Good luck !