Well, I'm guessing you don't have much in the way of violent runes yet, so you definitely want some energy/hp% runes. I don't know what is considered the best rune setup for her without looking at various sites (which usually differ anyway), but the key to using her successfully is keeping her alive long enough for her to recast the third skill (on herself if you're using her for Faimon), which is a complete heal. Awakening her and getting one skillup in it will get it 2 turns faster, but it is still 5 turns between uses, so you see what you have to shoot for. Fortunately she's the perfect element for Faimon, so it really isn't a huge undertaking to get her to where she can survive Normal mode, and then harder ones as you get better.
Also make her leader for Faimon, as the resistance bonus will help a lot with avoiding armor break. It helps a ton for a lot of things actually (Dragons), if you use a water team.
Higher end runes would involve violent for sure, because the more turns you take, the more times you can complete heal someone on your team.