Bf has an "attractive" female best friend that he travels with…

Hi everyone, I (22f) have been dating a guy (23m) for several months. I think he is super awesome and cute.

However, last night he asked me if we do become a couple in the future, will I be okay if he keeps hanging out with his female "best" friend (23f). They've known each since childhood and they basically hang out with each other every single day when he’s back in their hometown. They play games together, work out together and even travel together.

According to him, they had a thing back when they were in high school but it lasted a week and "nothing" happened between them.

I mean I did tell him that I wouldn't mind since they are like best friends, but I just can't stop thinking about how they sleep in the same hotel or Air bnb rooms during family vacations when they travel and "nothing" ever happens between them.

What do you guys and girls think? Is this just platonic or am I being gaslighted?