Lateral manuevers such as shoulder ins, side passes and half passes are great at strengthening the shoulder. More than anything I would try and get her to go straight and use both sides.
The over developed side will be strong and the other weak. You need to give time to the weak shoulder to get strong again before focusing on it.
Oops typo over developed*
What? A developed shoulder?
she had approx 1.5 months stall rest and 1 month in paddock turnout favoring one leg total for 2.5 months don't want to work on correction of this undersaddl due to her age and only working on her 5th ride under saddle however she can preform most tasks that I'd ask undersaddl from the ground with que