Showjump - I have the same problem as you in that my boy is very strong and sometimes won't listen to me in a snaffle (we just have a bash at dressage for fun!) I did try a test a couple of weeks ago in the snaffle which was a bit hairy, but somehow we got placed!
Several shows I have coming up are running "Have a Go Dressage" which you can do in any bit as it is non-competitive. I am going to enter these using his Pelham and see if we can progress to him listening in the snaffle out at shows (I school in the snaffle at home.)
Perhaps this type of Have a Go Dressage would suit you this summer for your girl? The one I have in a couple of weeks has a choice of 2 prelim tests and a novice test.
Hey Shellonabeach, have a go dressage sounds perfect but I live in a very non horsey area and coming across any sort of dressage comp within 2 hours drive from me is a miracle, but unfortunatly non do a have a go style class which would be perfect.
She has started to go really well in the pelham. Although we have been struggling with the basics for a long time, she is actually quite advanced with her schooling and half of me is thinking I should just move her from a pelham in to a double bridle and enter unafiliated elimentary. I just think doing elemetary in a double with control, even if we can;t do all the moves fantastically might be more enjoiyable for me that doing a prelim in a snaffle and not enjoying it because it's a constant fight. I don't really want to win at any level, just have fun.
There is a dressage comp in 3 weeks time that I think I might enter with a pelham but non competativly and see how she goes in the show enviroment *its a rc show so they should let me!)
HC or not, if the dressage is run under BD rules, a pelham is not allowed! There are many have a go shows now which allow any bit, martingales etc etc..... Or as you say, bite the bullet, put her in a double, school for a few weeks and see how it feels for you and for her and have a go at elementary......