Boyfriend Traveling with another girl

So essentially, my boyfriend is going to do a semester abroad in canada next year and he’s planning to travel around the states for about a month before hand. He’s going be away for about 6 months, and recently he’s begun planning to travel for that entire month with another girl who’s also going to canada.

She’s going to meet him in the states and they plan to road trip across the states for an entire month together and go hiking etc. I know my boyfriend would never cheat on me or even consider it, but this girl isn’t very nice and never accepts the word no for an answer :( I just don’t like her personality but she’s a friend of my boyfriends.. I just feel weirdly uncomfortable about it??

I’m not going to tell him he can’t travel with her because their friends and that’s insane of me - but i can’t get over the weird feeling i get when i think about... Makes me feel sad and sick at the same time :( What do I do to move past this feeling?

He’s so excited, and i’m excited for him but I want to cry every time she messages him (frequently) about planning their trip together... :(