At Lv50, which you mentioned she starts one shotting, no she wont. I know from self experience. Using a dark team with no HP boost from eidolon (since there are no SSRs with it) and only HP from the union buff, my team has around 10~12k HP each. A regular or enrage overdrive will not one shot my team unless they're already extremely hurt and one that's debuffed with atk down one will do even less so in addition to own defensive buffs.