I'm not sure about the dissociation, so I'm not help at that, but regardless of whether she is or isn't I think you have the right idea with the psychiatrist. She definitely seems depressed, and it's totally understandable why. Also, if her father did do more things, she might be embarrassed telling you, because who really wants to tell their mom details about sexual stuff they've done (bad or good)? Maybe she would feel more comfortable with a different therapist (did she like the old one?). Anyway, when you do get her a therapist, I would definitely bring up the accent thing because it doesn't seem right, either, whether it's dissociating or not. Also, this abuse is (understandably) causing her a lot of mental pain, so it would be best to deal with it as soon as possible so it doesn't turn out to be something longer lasting like post traumatic stress disorder.

And as for your sons, I would sort of recommend that they at least go to their own therapy sessions, at least a couple times, just so they know they have the option too. I know sometimes it seems like people deal well, but some people (especially men) feel it is "weak" to show how they really feel. Alcoholism affects everyone involved with the one person who has it, which also includes you. I hope you also take care of yourself and do whatever you need for yourself. You seem very strong and like you are an amazing mother, your kids are lucky to have you. I'm sorry you're going through all of this, and I send my best wishes.