IMO I don't think she's trying to bother you. She's probably is concerned and thinks she's a good motivatior. Maybe she should become a personal trainer. When I see an person who is heavier working out - I think wow....look at the motivation...good for them!!

Look at the people on those shows like the biggest loser and the one where they're trying to win a wedding - some of them are wearing spandex. Don't care about what people will say and just start exercising. You should tell her nicely how you feel but I really think she's trying to get you motivated.