Really considering changing doctors who does this or suggests this?
Speaking as a nurse, she is acting irresponsibly and I would make a very big stink about it. No patient deserves to be spoken to with sarcasm. Ever. Additionally, it is completely inappropriate for her to be making recommendations for medication changes. It's not covered under her licensure and she does not have the training. A nurse in that role should be communicating with the doc the FACTS: a) You are having RNY surgery (date and with what surgeon/hospital) and, b) according to the WLS surgeon you can no longer take the sustained release formulation of your Wellbutrin and need another option. The end. It is not her job to make recommendations to your OR the doc about what the other option should be.
Also, if the situation has an urgency to it (your doc is out this week and you have surgery in 2 weeks), she should be offering to have whatever doc is covering yours look into the situation and see if a 2-week Rx of an alternative med/formulation could be written until your doc gets back and up to speed on things.
Also, from your description it sounds like she's not actually reading your file before/when she's talking with you about your labs and medical history. I think it's time to tell your doc all of it. Yes, talk to the practice manager, but TELL YOUR DOC. Tell your doc that if it's not dealt with, you'll be leaving the practice. Docs don't want to lose patients (it affects their $$) and they REALLY don't want to lose patients because of an incompetent nurse or office staffperson.
Come visit me on my blog, Through a Cooking Glass! I talk about my journey through WLS and learning to live, cook, and eat on the other side.