I'm 21 now but when I was school I became a "buddy" to many of the younger kids. But that was it. I offered advice and guidance for students younger than me, mainly how to balance with exams and curriculars etc. I am still in contact with 2 of them now because we're in the same social/volunteer groups so it's kinda unavoidable, but never have I felt a need to go out of my way to find them to spend time together.It is. She needs help at this point. You can spending time with younger people but here it's an obsession, and it's the fact she willingly search younger people which is creepy.
The way Ruby is acting is just, for a lack of better word, weird! The obsession with being younger is suspicious at this point.