She can drain power and life from people. She can make other people more powerful by feeding it to them -- superpowers. She can herself run faster and be stronger on the same principle, to a superhuman level of ordinary human skills. She can NOT cure anyone of anything, even exhaustion, by feeding them the power.
She's not going to find out whether she can kill this way, not this novel.
But can she feed people power so they can do superhuman versions of human things? It may affect the plot. Hmmm. . . .