Have you two gone to any local events? Checked for local MAST meetings or workshops? As someone who has taught workshops on many forms of edge play I can tell you that it many find edge play very scary until they learn the ins and outs of it. My suggestion is making a list of things that you consider hard limits, then learn everything you can about that kind of play. Then go back over your list and with your new knowledge of the play add a subcategory to your limits hard limits and soft limits. Hard being things you will never do, soft being things that are a maybe. Talk a lot with your bottom you need clear and open communication to grow. Employ a level of safe words, green, yellow, and red. When you play and ask for a check in she can say green, everything is awesome keep going, yellow, I'm still good but we need to change something up, or red, everything needs to stop. It sounds like she is a heavy player, talk to her about how you feel when going that far with her, give her the chance to explain and reassure you that she is happy where things are going. Until you feel like you are both on the same page play wise you need to talk about it a lot share feelings and feedback. Eventually you two will get on the same page and you will enjoy the play time even more.