She's cool, and although she's no longer in my top 20 stat-wise, I tactically make use of her in my red boat's vanguard team for her triple strike against the semi-boss Chance panel pest in harder slash-type whaleship maps. It helps that she has skill activation boost, too.
Specifically, just to add on to what's been posted, it is the effect of the trainable ability Healing Boost, which permits girls who wear that ability to literally go "over the limit" if they have HP-draining skills or pass by panels which restore HP (e.g. healing springs, chocolate statues from Choco Cosmos/Lantana, or even heals by passing through nests).