What the fairy godmother put Feona (or how ever you spell her name) in the castle in the first place?

It just says she had a curse put on her by a witch and they locked her away in a tower, and Charming is the godmothers' son. Wouldn't that benefit her financially? So just throw her in a tower until she's good and desperate enough to like your ass wipe son? And last I checked in kids movies witches and fairies had the same skill set.

My kid and I are sick and were watching movies btw. I'm beyond bored lol.