She reminds me of ....
A young Bridget Fonda.
Just saw the pilot episode of Supergirl, and I think Melissa seems to have the same super adorable nervous energy as the lovely Ms. Fonda. Kind of the same cute lip thing going on too.
http://www.wingclips.com/movie-clips/it-could-happen-to-you/promise-is-a-promise
For those of you who don't know who Bridget Fonda is, man I'm old :)