I'm going to ask a girl to change her trip
I'm confused, why do you think that you need to tell her to change her trip plans?
Because another year with this family is too long
I don't think that is very nice of you. You shouldn't get in the way of the plans of others. You should really talk to her before you ask her to change things just to suit you.
She said it's okay so feel free not to judge my actions.
You're lucky that she is okay with it, but if it wasn't okay with it she may be hurt with what you have done, so I still do not recommend you change plans of your friends or other people, specially if you do not have anything to do with that plan or trip. I hope you just focus on your own plans and what you can change with your own.