Double chainer with mild healing.

A-

(S+ at BT2)

+Double chaining offers the highest possible damage output in the game in scenarios that require burst

+Access to acceptable heal

-Double chaining cuts ATK, which causes it to scale worse than it seems as the game goes on.

-Extremely dependent on ally conversion (meaning she can drag down your team's CDs)

-CD/non-preemptive is awful without sufficient BTs

Double chaining is an extremely powerful effect, but it can often be a lot of trouble for your team due to its slot-hungry nature. This puts double chainers in a bit of a weird spot, perhaps akin to that of healers: in the right situations, they're absolutely necessary for pushing through OTK damage checks, but in the wrong ones, they're a wasted team slot. This is also why Double Chainers are possibly the most BT hungry 5*s after cross converters; at BT2 onwards, their damage with only one other DPS is enough that you can run them as a secondary DPS, which offers more team-building flexibility and less in-game liability.

Louise's main feature beyond double chaining is mild healing. It's not nothing, and it scales well enough in whale comps that you can sometimes skimp on an actual healer or make riskier plays. This is probably enough to carry her towards the top of the 5* double chainers, even if she lacks the stats or synergies of the other chainers. Note that Louise is particularly dependant on MBT because almost all of forest's best converters have 3CD actives.