Booked tickets to visit without asking and now what?!

MIL and FIL live in Florida and her father lives here with the rest of the family. He moved here last summer and does have health issues that his family helps with. She is the only daughter of his, and is who handles most decisions, etc. She told the entire family that she was planning on coming up in July, and they told us, laughing, saying how she just does what she wants with no care for anyone else. I laughed and told them “well, Hubs will be away for military training and she knows that, so she better find somewhere to stay”

Two weeks go by, I’m waiting for the Inevitable, we speak daily yet she has made NO mention. This past weekend I receive a text with booked plane tickets and an “im coming home!” Text. I look at the dates. Almost to the day, the dates he is away. Comes in the day he leaves, leaves two days before his return. I have plans throughout his entire training time plus work 42+ hours a week. I remind her he won’t be here and I have plans, and she’s entirely dismissive and says she’ll help out, she has to come For her dad. But what part of helping her father does helping around the house or dinners and drinks and stuff accomplish..?

I talk to my fiancée and explain how she cannot book tickets and assume she can stay, that we were not consulted and he agreed that if it were my parents he wouldn’t accept it. My parents would never do that, though. So now comes the awkward “well now what..?” I told him he needs to talk to her and express that this is our home and she cannot just tell us she’s coming and I have plans, but he said I can tell her too. I said no, it’s your mother and she needs to learn boundaries from
You not from me. I’m so uncomfortable and the worst part is, if she had asked, I would’ve appreciated that and probably would’ve said ok.

I don’t want to be ostracized but also don’t want to give up my plans and time for someone’s bad choices. Idk what to do.

Booked tickets to visit without asking and now what?!