PS - if Leaders really are shouting at the girls to 'shut their bloody gobs', and stood smoking outside in front of the girls, and they are not doing any badges, or anything else - then you should complain to the District Commissioner because that is NOTgood enough, and you are not getting the service you are paying for.
I'd urge you to complain, even if you decide to withdraw your daughter, because that needs to be put right for the other girls.
Unfortunately, Brownie units (as with Cubs, Scouts, Guides etc) are only as good as their (volunteer) Leaders, and the activities tend to be what the Leaders are good at, or enjoy. I'm a DC, and am aware that there are some units which are much better than others, and feel so sorry when I hear stories like yours, where Leaders are not providing a great experience for the girls.
In an ideal world, you'd have a team of Leaders with complementary skills, but there's such a shortage (for Guiding anyway) you can't chose who leads a unit - you just take what you can get.
Totally agree about DD needing her own space, but you don't need to volunteer on a permanent basis - Leaders would be grateful if you'd just volunteer for the occasional evening (even as a one off). Or you could volunteer to, say, provide a regular (weekly/termly) newsletter to parents so that they always know what's going on - and could then volulnteer to help with activities they have an interest in.
Just saying - we desparately need more Leaders in Guiding (either in or out of uniform/regular or occasional volunteers) 