Because malgus is the easy one to kill?
Malgus' shatterpoint would be his weakness in respect to Force Drain, she'd realise he's the only one she could best one to one, without Vader or Kun receiving serious injury. She'd help Malgus because she has to if she wants to win.
And it's listed as an ability, I think it's called Essence Transfer, or something along those lines. Maybe Vital transfer? Might be Vital transfer, I'd have to check and I can't be bothered waking people at the moment
Either way, the power is listed in the guidebook which details each individual power, as being the ability to transfer her life or Force essence into another being.
Dark Transfer you mean.
Also helping Malgus is just going to weaken and distract her, she isn't gonna be able to keep up if she is halving herself by sharing her power with another even if that. All that is gonna do, is leave herself more open to being killed and why would the 3 ignore her anyway?
What are they just gonna ignore her and do nothing? That isn't smart.