When is your next group session? If your group is today, then yeah, I'd wait until group today so that you're not spending $$$ on crisis care that you may not necessarily need. I don't think waiting a few hours would make a difference since you could try to use coping mechanisms in the interim. But if your group isn't for a while, then how long do you think you could hold out? Do you have safety plans?

Also, you should try to contact your pdoc and ask about the Ativan. If you are adamant about taking more and you can't wait for your pdoc, then can call your pharmacy to ask how much you can safely take, as pharmacists are legally required to know max dosages etc.. However, I would still advise you contact your pdoc ASAP.