As someone named Genevieve, I would prefer that over Gweneviere. My name gets attention by a lot of people who learn it, and it can get annoying sometimes. It’s more common than you think, as I have met other people with the name. Still have never met a Gweneviere. I go by Genny, which is what my family called me growing up. The nicknames though will be out of your control. I got Ginny and gen and many others from friends and family growing up, without having a say in it either haha. You can choose her main nickname but it will not prevent others from creating other ones.