Vanessa would definitely be on the young end if she’s somehow both a medical student and Maggie’s long-lost daughter, but a medical student with a connection to a nurse in the same season that Maggie is interested in reuniting with the daughter of around the same age seems like it can’t be a coincidence.
This is a scripted TV show, after all!
Vanessa as the youngest person in her class could mean that she’s in her early 20s, which in turn could mean that her age would fit with the daughter that Maggie gave up 20 or so years ago when she was a teenager.