If Pippa did get a Holo collab, I very much doubt it would be with Fauna. Fauna has stated multiple times that she is very unlikely to collab with anyone outside of Holo (I assume she means in a 1:1 capacity, anyway. She probably would do a big collab if like Kiara planned it with Niji, or whatever, I bet). Neither Fauna or Pippa would initiate one themselves.Pippa did great with her Henya collab though, they've even talked about doing a Mahjong collab next week. Maybe she'd do well if she ever got her Hololive collab too.
Calli or Kiara would be far more likely, and even with them, with Kiara it would have to be something like Pippa tagging along with another girl who already has interacted with Kiara on Twitter and done something that made Kiara want to collab with them. Calli is just too busy.