Is there a scan of her switching identities? and a good reason as to why, besides there already being a Supergirl?
Got any pictures of her as Supergirl? preferably not from where she 1st meets the other Supergirl.

If you mean the current powergirl dressing as the current SG i don't think there are.

No before she was Power Girl

Nadda. She's been that since her debut. No red skirt, no blue blouse, no red boots, all that she's worn is what she wears now.

Thought she was Supergirl n Hidden or something

Well in a way she is Supergirl...but no she has not taken the identity I think

I don't think she was ever Supergirl. She's always had the identity of Power Girl from what I know.

Though she did go as Nightwing for an arc of Supergirl.

Hmmmm... (thought bubble) Power Girl was in a fight and her costume is trashed. She is near Smallville so she decides to make a pit-stop. Another emergency happens and she has to leave. Ma hasn't been able to repair/clean Karen's Power Girl costume yet. Ma gives her Linda's (Danvers) old Supergirl costume instead (the white bare belly T and blue mini skirt).