I struggled with this several times as a sniper before I gave up trying to damage her conventionally and relied totally on the healing circles to bring her down. Just keep kiting her round, run round the outside of the healing circles as they appear and as her violet circle crosses into it, run towards her and trigger the healing which will also do her some serious damage. You'll probably need to do this 4-5 times to wear her down. Since you're not damaging her you'll never hit 30 stacks and won't have to worry about avoiding her force overload.
