Fantasy series I read in the 90s/00s. There were many books in the series and one in particular was about a girl finding her magic.

[Katie]

Her specific magical powers were that what she wished for came true. But only if the person she was wishing for didn’t know about her magic.

She didn’t know about her own magic and wished she was a princess and had a family. Those wishes came true but then her magic stopped working on herself once she found out about it.

[Sue]

There's a character called Ida in The Colour of Her Panties, in the Xanth series by Piers Anthony; whose ideas come true. https://xanth.fandom.com/wiki/The_Col...