While 115 maybe the lowest listed for 5'4" small frame... that is probably an average of some kind.... some small framed women are a lot tiny that others... and 112 maybe fine.... I think anorexia has been in the news so much people are aware of it... it could also be a smidge of jealousy ... though if you work out, you may gain more weight, but it would be muscle tissue which will help define you in another way.... If your doctor feels that you are healthy and you feel good and have the energy to do what you want.... then all is good with the world...

just for health sake, make sure you body fat percentage is at least at the minimum if you are having any trouble with lack of menses.... which also helps when sick giving you the reserves to go on.....