Why won't your trainer let you take lessons with anyone else? So she is a dressage trainer and knows you are an eventer, and she knows you need some help with your jumping, and she won't let you get the help you need?
An instructor is supposed to encourage and help you along, and when/if something is out of their realm of knowledge, they should direct you to someone who CAN help you. I obviously don't know specifics of the situation, but I'm just kind of confused about how you are supposed to learn and grow as an eventer if you are only limited to help in one of the 3 disciplines. You need such a broad range of skills in eventing, it seems really backwards to me.
Not trying to be rude, just curious.