I am a coordinator for a Canadian therapy dog organization. One of the things I do is help out and train new volunteers and dogs after they pass the initial test. I accompany them for the first four to six visits to make sure they, and their dog, are comfortable with visiting.
On the first visit, just the volunteer comes and leaves the dog at home. He/she gets a tour of the facility (usually a nursing home), gets to know the layout and staff and speaks to some of the residents.
The next visit, the dog comes along. A dog's first visit usually doesn't last anymore than 15 or 20 minutes. As you saw, a dog can get pretty overwhelmed, pretty quickly. I find that on the first visit, most dogs barely even focus on the people because there is so much going on and everything is new.
The next visit can be up to 30 minutes as long as the dog doesn't indicate it is stressed before that. By the second visit, you quite often see a real difference in the dog in that they start to focus on people a little more. Like Carina said, if you take along some treats with you and have the residents feed the dog a treat, the dog comes to recognize this place is fun!
The following couple of visits are all about 30 minutes as long as the dog is okay with that. If a dog does great for 20 minutes, then starts to get a little stressed at 25 minutes, no problem, we listen to the dog and leave. I've found that usually by visit number four or five, the dog handles 30 minutes just fine and has figured out why he is there. :)
At that point in time, when both volunteer and dog are comfortable with their 30 minute visits, they can start visiting on their own without my supervision. By then, the volunteer can gradually build up the length of visits, still being careful to watch the dog for signs of stress.
I think what happened with you is that you unintentionally overfaced your dog on her first visit. It is very easy to do with all the people clamouring to see the dog. It's hard to say no and disappoint people.
If you decide to give it another try, explain to the volunteer coordinator that you'd like to come in for just 15 or 20 minutes and slowly get your dog used to everything. If there is someone in a wheelchair, try and take her to them first and have them feed her a treat if possible. Watch her very closely and at the first sign of stress, get her out of there. All new therapy dogs get stressed, this is not at all unusual. If after five or six visits, she is still stressing out very quickly, then she may well not be cut out to be a therapy dog. I don't know how old she is...if she's young, she may need more maturity before you try it again. I would definitely not give up after just one visit though. If you know a very experienced therapy dog handler within your organization, perhaps they could come along with you and give you some tips?
By the way, visiting with children, troubled or otherwise, is a whole lot harder on a dog than a nursing home and it's not something I'd recommend for a new therapy dog. Our organization requires the dog to pass yet another test before they are allowed anywhere near kids, even if they're very experienced visiting with adults. Maggie is certified to visit with children. We've done presentations at schools with the SPCA and we've visited with mentally-challenged teens. Children are often rougher and definitely louder with a dog than nursing home residents!
