It probably should be pointed out that Gypsy's are a relatively new introduction to the US so the OP having an 18-20 year old one when she was a kid is probably kinda unlikely.
I definitely agree with Gin.
Another option is that she was some kind of draft mixed with a Shetland (to account for her small size), where there's a will, there's a way! Haha
Or, there's always the option of draft x generic pinto mutt pony. Mutt ponys seem to be relatively common as kid's horses...
She was adorable, whatever she was!