"She lost interest" means she got bored with it....wanted to do something else instead. If I'm playing a game and lost interest, that means I did not want to finish the game - I wanted to do something else instead. Or I might have a boyfriend but I lost interest in him, so I might look for a different boy friend. She got over it soon" would mean she was experiencing a mood, or emotion that did not last. She was angry, but got over it soon. This is different from losing interest.

But she GOT over it very soon.

No. Get over - climb over the wall, or keep the problem under control. Use here " out of interest"