In general, you want to stay as healthy as possible whether your avm is treatable or not. This includes diet.
High fats and sugars will make you feel icky so you'll want to try to eat a well-balanced diet of fruits, vegetables, meats, and dairy.
One thing to keep in mind is having an avm can cause nausea. It may be difficult to eat anything at all if you don't feel good. In this case, try to eat when you can - try high protein shakes or smoothies and similar items in order to get some calories and allow you to stay strong to fight this issue. You always want to keep your strength up.