It took several months, I can't remember quite how many, but at least 3-4 months, between the referral and the appointment, which seemed like an eternity...
I don't check for wounds but I do notice when she's done it, she then becomes very careful about covering up, whereas normally she's quite happy to walk about the house in her underwear. I agree that it's an invasion of her privacy and perversely might push her into self-harming more.
I know, and I understand, that your first instinct would be to do everything to prevent her from self-harming, that's natural, but one of the advice I've seen is that you shouldn't try to stop her as it's her way of coping with her feelings and she probably does find it helpful, however crazy that seems to you. The advice is to try and help her to find other ways to cope with her feelings.
The other thing that you can do is show her how to take care of her wounds, by keeping them clean, and explain to her the importance of avoiding infection.
I do sympathise, it is very very hard to take and to cope with as a parent. Hang on in there...