I've never thought of Lalla Ward as embittered about Doctor Who
. Oh, true, she and Tom Baker won't be in the same room, and she's no fan of Matthew Waterhouse, but she's been quite active with Big Finish and you could argue that her association with Doctor Who
(specifically, knowing Douglas Adams) led her to meet her current husband. Heck, she even recorded dialogue for Ian Levine's animated "Shada."
For a long time, I'd have said that Janet Fielding was the most embittered Doctor Who