Try not to let it get to you. Your friend may think they are helping you. However as you said, she can't blame all her problems on a surgery if she's not being compliant with the dietary guidelines. I'd just say look, my procedure is not exactly like yours, there's no malabsorption, and I'm doing this, so please support me, or let's not discuss the subject any more. She'll realize you are confident in your decision and let it go eventually.