Couldn’t agree more wrt what’s it going to be like when you have children, because as much as I sympathise with not liking confrontation/being a people pleaser, you have to think of controlling people like this as giant toddlers.
If you, a grown adult, wanted to put your own Christmas tree in your own home up on a certain day, and your toddler kicked off, screaming and telling you not to, what would you do? Give into their demands just to shut them up, or because you’re scared to say no?
Of course not (at least I hope not). You would say “I’m sorry you don’t like it, but it is going up today because I’m too busy on Sunday.”
How other people react to YOUR boundaries and decisions about YOUR life is THEIR problem. They don’t get a say in it. You cannot control anyone else’s opinions, or their reactions, so don’t try - and absolutely don’t appease them just so they won’t kick off. That is a slippery slope to a world of pain, whether you are letting a child, a teenager, a grown adult or, in this case, a tantrumming toddler in an adult woman’s body.
Draw your line now and stick by it, or things are only going to get much worse.