Pros are that it is a very low cost activity compared to other sports or activities, It can feel like more because it isn't just a one fee thing, it's $12 in our area, to join, then what ever it is for the uniform under $20 I want to say 8, and the place might have dues for craft supplies again for us $10 per year or a fee for an activity/field trip we found a lot of free or low cost ones. but still $50 for a year of free babysitting!!
Cons- girls scouts is not structured where it will provide the routine it sounds like your child needs. if she needs to know what exactly is happing next and can't handle going with the flow it might be tough.
Our troop had a typical routine
come in a do a coloring art type activity as everyone trickles in
say the promise and pledge the flag
discuss what the adults had planned based off what the girls said they wanted to do last time,
do an activity like a science experiment, a cooking thing,a craft for a nursing home etc.
then usually a game or song
then a closing to talk about what to do next time or down the road.
but we get side tracked ALOT by responding to what the kids like or don't like.
She can earn badges for the activities each one usually has 3 things she has to do.
if they do a Journey which is several badges around a theme there may be a lot of listening to readings and discussions of the broader topic. if you pm me I can show you some of the ones available and ones we have done.
because there is so much individuality between leaders and troops, you may find some are strict about earning the badges and some just hand them out.
Best thing to do is Google Girl scouts. find one in your area, ( call your local school or church or something and ask around if you can't google it) and ask if you can just have your dd try one meeting with you in attendance to see if it will fit.
if you volunteer to be a leader you can control ALL of it and decide how you want to handle the badges and the meetings. It could be just the perfect fit for your dd and be fun for some other girls too!
If this isn't sounding good to you, then I would suggest talking to her doctor/therapist/guidance counselor at the school and asking for suggestions on local activities that would be a good fit for someone with her challenges. We have friends whose son really found his niche w ROTC in Highschool. I know there are summer camp programs in our areas for kids with special needs that work on skills for their particular issue. the drs might know of them.
Good luck, I think scouting is great, but it might not be right for all so do your research and do a trial run.