Wendy got her big break on the soap Crossroads. After Who, if you need more Wendy (and of course you do), she was also in the last few series of Freewheelers (aka Avengers for kids), which, unusually for her, are the only episodes that aren't missing.
She also appeared in a few movies, most notably The Blood on Satan's Claw, a 1970 cult horror film, alongside Anthony "The Campest Master Until the TV Movie" Ainley. It's considered a classic example of "folk horror" (think the original Wicker Man, or the village that Hot Fuzz was parodying). It's also often considered Piers Haggard's best work before his Quatermass revival, and was an inspiration on the writing of Mark Gatiss.
Oh, and Wendy has a topless scene in Claw, but I'm sure that's not why so many people download pirated copies of it.
After Freewheelers, she retired from acting to become an agent for other actors like Nicholas Courtney, Mark Strickson, Colin Baker, and Matt Smith, all of whom are perfectly fine actors, but she ruined their careers by steering them toward Doctor Who anyway. She even sent her own daughter Charlie to work for Big Finish.
Wendy returned to acting for a few roles later in life, most notably a recurring part on the soap Emmerdale opposite Frazer Hines. During the wilderness era, people like Paul Cornell would get jobs writing for Emmerdale because it was the only show with Jamie and Zoe in that was still on the air.
She married Melvin Hayes. Yes, a man known for playing panto dames and Gunner Gloria Beaumont did better than you ever will.