Fun is definitely imperative for Pokemon. I think Tera might just enjoy having a friend of the same species around. The only other Spiritombs she's ever seen are her own children, after all.

[It's probably a good thing John doesn't know about her ties to Team Rocket...this conversation would go very differently.]

It's nice to meet you, Perona. I'm John Egbert uh...Ghost Specialist? Hehehe...