My son was diagnosed ADHD (with mild dyslexia and auditory processing challenges) at age 4 (he's 7 now); my daughter was diagnosed with sensory issues, dyslexia and anxiety at age 5 (she's almost 10 now). I have been in your shoes.
The best support group I found was the CAARTE parent training class I took at Shelton School when my daughter was enrolled in Kindergarten there. My ADHD son was 3 then, and I was pregnant with the 3rd child who thankfully doesn't appear to have learning issues so far. Shelton still offers those classes each semester, open to the community, not just parents of Shelton students. You might call other schools for learning different children that are a little closer to you. Those parents are the most supportive I have found.
Another possibility will be through the OT clinic you end up in for SI evaluation and treatment. The waiting room during twice weekly OT sessions is almost as good a support group as anything else.
You are probably in the middle of the hardest 6 months of this whole process. Hang in there. Once you figure out what the issues are, make a plan to address them, and start implementing a lot of small changes in your life, things will start to get better. I don't believe in magic bullets. Every person is extremely complex, and what works great for one kid doesn't seem to make a difference to another. I find it comforting to keep a long list of things I could still try, because feeling like I have no more options is probably the worst thing for me. You compile that list by talking to other parents. Specialists are great, but they often only see what they are trained to treat, and they have their favorite way of treating it. Only you have the bigger picture in mind all the time. Your daughter needs you to keep your eye on the ball - she will be a terrific adult ...if you can all get there in one piece!
If you would like to hear more about the things we have tried and what works for us, please send me a message.
S.
SAHM of 3