Mom had good bev hills blepharoplasty. Went for eye exam dilate. One lid drooped more for 4hr. Due to wrong dose or muscle? Her dad had oc mya gravis

Eyelid Drooping. Most pupil dilating drops are parasympathetic antagonists that act by paralyzing the iris sphincter muscle. It is possible that the medication also relaxed (or temporarily paralyzed) one of the small muscles that elevates the eyelid - likely mueller's muscle which lifts the lid via sympathetic stimulation (opposite the effect of dilating drops). Get it checked out if symptoms recur on their own.
Have her evaluated. If this resolved after the one episode, it likely is related to the eye drops. If this is something that has occurred before, she should be seen. Since she had eyelid surgery, there has been an alteration in the way the lids behave, and this may make it more difficult to evaluate. It is best to have your mother checked out by an eye doctor.