I would release him wherever she found him. You'd be surprised how their instincts kick right in. Tiny wild caught babies are tougher to care for than captive bred frogs and toad.
Just tell her wild froggies do better in the wild and that they sometimes die when we take them from their homes.
Not a bad effort on your part.
Do you have any frogs of your own?

We love frogs

. They're all so different. If not, I bet you'd love one. Best thing to do is research which you'd like best by their general characteristics and overall behaviors, see what their care would entail, and what kind of home you could or would like to provide for them. There is a great article here about which frog is for you. I forget the exact total, but it's a great article. Might want to see if you can find it. I'm not sure how to link it from my phone, which I'm on.
Good luck!

He's a cute little one.