Her house, her rules. If it were just that she didn't want the annoyance it'd be a different situation (still her rules, but it might be more appropriate to put together a case for you to get a snake), but when someone has a legitimate fear of an animal you're talking about serious mental sacrifice on their part to have it in their house. For someone with a phobia, having a snake in the house can be a serious ongoing stress, even if they agreed to work on their fear, and that's a lot to ask of anyone.