I think she looks like a Belgian cross as well... her head and neck are what make me think that. She's only 3, right? She has plenty of growing to do, so I wouldn't rule out Belgian being in there just yet.
Personally I think she looks kinda morgan to me. She has some height to her though. Her butt shape looks like my belgian cross. Belgians are a slow maturing breed so it is possible she is a cross and will thicken up with age.