If she's young like she seems appearance-wise, she either has no life outside of what she does with them (to have such an open schedule to do things whenever / wherever and probably no other job but this), they're paying her ridiculously well, AND / OR she's a closet stan (who happened to find this gig) so she's all gung-ho to do anything they want.
Like some have said as well, I doubt she's from an agency. Unless it's a really loose agency. One would think an agency would have parameters as to what someone could do or couldn't do, hours available, where she could go, what she could participate in, staying overnight all over the place with them, etc. !?!?