Ouch.
You're both adults and part of an adult relationship is recognising the full being of another person.
She doesn't recognise you as a full being, does she?
I think you need to arrange a coffee with her in a cafe (neutral space; both of you together as people, with no children) and have a chat about how you feel.
Standard advice for those conversations is to use 'I feel ...' a lot, and listen.
It takes the sting out of what you're saying and makes things more collaborative. It leaves an opening for her to say things like, 'I had no idea ... I've been so busy, I didn't notice ...[and ideally] I'm sorry I made you feel this way.'
It will require yet more work from you, which may be a bit irritating - but it may get there outcome you want.
Be clear before you start about what you do want: amorphous goals like 'more consideration; appreciation; being treated like a human, not a slave/apparatus like a washing-machine.
Less of a workload.
Being included in affective activities, not just used for childcare.
More warning about schedule changes.
Realistically, this is only going to work ^if you, yourself, work on your own boundaries.
Yes, you are being exploited.
No, you can't just say that (sadly).
Something has gone wrong somewhere for you to end up in this situation.
Either you have picked up that she is a bit scary and you are worried about - what? Not seeing your GC? Her temper-hostility? - if you say 'no' to anything
- or you generally have low self-esteem and constantly let others set your boundaries for you.
Or it could be somewhere between those things. Or something else.
It's a very difficult situation.
In the past, I have been in your situation with friends. Sadly, I ended up walking away from those friendships. Obviously, you can't do that.
It's hard, hard, hard. You have my sympathy.