She finds it kind of sickening, but also weirdly endearing. She's more put off by Cy's general attraction to young girls than she is by him using her pics in particular. The fact she volunteered those for that specific purpose probably helps- she sleeps better at night knowing he's no longer looking at his students, and it's oddly flattering he was ready to delete all the pictures he'd accumulated of them just to look at her instead. Also, while Lynn had quite a happy childhood, she's very glad to be a grown adult, so she doesn't care much about her memories being used like that.

She also has a tendency to keep kind of... copies of herself at different ages in her mind? Some things she does to please her kid self, some things she does to please her college self, and some things she does to please her grown self. So while she's obviously not a child anymore, she feels that when Cy's looking at her childhood pics, he's looking at her.

All in all... A bit of a messy situation, but much preferable to Cy continuously collecting pictures of his students they might regret later, in Lynn's opinion.