So our invites went out at the end of August, RSVPs due last Friday. When FI's aunt and uncle and cousin (separate invite because he's an adult) got their invite aunt immediately called and asked why said cousin's gf was not invited. A) we didn't know he had a gf. They live hours away from us and they don't keep in contact with FI or FI family unless they want something so how the F would we know he had a gf??

she has apparently only been his gf for a month MAX. So we did the whole "sorry but due to budget, space blah blah blah" thing. Fine. Great. Whatever. But they still didn't send their RSVP back.
FI just text me and said cousin is now engaged. Are we now supposed to go back and say it's okay to bring her? I know this is stupid but I really want to say no just on principle and the fact that they don't even like us and they got engaged after the invites had gone out and we really do not have the space. Am I just being a betch lol?