I take it there is at least one other person living in the house with you, if they were coming anyway even if you weren’t there? Otherwise why would they come to stay.
I do think you need to reframe a lot of this stuff in your head. You’re complaining that you didn’t like them coming in and making themselves a meal. But plenty of adult children would have arrived and sat back and expected to be cooked for, even if they’d said originally that they wouldn’t need a meal. You haven’t made It clear HOW they went about making this meal and that makes a huge difference. Eg they might have arrived and said “oh we’re so sorry, I know we said we wouldn’t need a meal when we arrived but we’ve had a nightmare and the chicken we had in was off when we opened it/DH had to work late and the baby was screaming and wouldn’t be put down so we decided to leave early in the hope the car journey would send her to sleep. No, don’t get up, we don’t want to put you to any trouble, we’ll make it ourselves, just let me know if there are any items in the fridge we can use. We’ll replace it tomorrow if it’s earmarked for tomorrow’s dinner. Have you already eaten? Would you want some if we make it?”
If that was the way it panned out then they seem like perfectly nice, well-mannered and thoughtful people whose lives are a bit frantic with work and a young baby and who would appreciate a warm welcome when they return to the family home.
If, however, they just barged in with no apologies, didn’t ask if they could use anything out of the fridge, used the specific food item you had planned to use for a meal next day leaving you short, with no offer to replace it, left a mess in the kitchen for you to deal with, didn’t offer to make you some or checked if you’d already eaten, expected you to mind the baby while they both cooked, etc etc, stayed up late being noisy and keeping you awake, then none of that is being remotely thoughtful or well-mannered and would piss anyone off. Oh, there are weirdos on MN who insist that they like having their house taken over like that by their adult children and love the noisy chaos it brings. That they don’t mind it when they bring loads of random people back from the pub while they’re staying etc etc. But to me that’s just getting walked over. It’s incredibly rude and entitled, Close family or not.
That’s my take on it, OP. If it was done in the first way then I would count yourself very lucky you have brought up such a lovely thoughtful daughter. Second scenario, they need telling to grow up and be more considerate.
How do you cope with your DH doing his own thing which may impact on you, out of interest?