PEOPLES CRAPPY COMMENTS ABOUT WLS!!!

It sounds to me like she is concerned for you and bringing up everything she has heard about (as opposed to researched) that is dangerous about losing weight quickly.  When she starts bringing up the whole heart thing, I'd ask where she did her research just to point out that she is acting upon what she has "heard" versus what she actually "knows."  Then tell her you are under a doctor's care and your weight loss is "typical" under your cir****tances and that you are regularly checked. If she continues, then there is something more at the root of her concern - and if she is a good friend, I'd try to address it.  Perhaps your experience can help her?