Honestly even if she doesn't have to go through pregnancy I wouldn't put a mare that age through the stress of simply getting an embryo out..
Also think it's one of those things if you have the knowledge you don't have to ask.. shrug.
Do you have pictures of the mare? Is she 30 years young or on her last legs? I would definitely pass.
It is a stressful expensive option though.. something you do for VERY nice horses that you don't want to risk or lose pregnancy time.