The role of being in a position of power in acquiring karma

She never had what it takes to punish anybody

At least in the Western societies that I am in, women may an immense "power", for better or worse -- but often within a family or a circle of friends, instead of "public life".

she was too weak to kill anybody

I think that, according to Buddhism, your intention is important. Her actions aren't unimportant, but you don't mention her motive: is she kind or malicious, selfish or generous, does she intend to benefit people or to hurt them?

who got the better life

I think that Buddhism teaches generalities about karma -- i.e. there's good karma, bad karma, no karma, and that karma is intention or intentional action.

But karma is complicated -- there's a lot of it, good and bad -- and it takes supernatural powers to see how karma plays out, and whether someone goes to a higher or a lower realm after death, i.e. the Buddha could do that but other people can't.

In the same way, there is the case where a trifling evil deed done by one individual takes him to hell; and there is the case where the very same sort of trifling deed done by the other individual is experienced in the here & now, and for the most part barely appears for a moment.

[Lonaphala Sutta: The Salt Crystal (An 3.99)](Lonaphala Sutta: The Salt Crystal)

So this kind of question -- about the precise workings-out of karma -- may be unanswerable. Especially when the people in question are fictitious.

According to karma, who got the better life, that is, the life more likely to be reborn as either a better human or a being in the higher realms?

Well, Bob will get reborn into some of the most beautiful Heavenly realms, enjoy the most wonderful life there for a while and then get reborn into some of the most horrific hell realms and suffer tremendously; while Alice will get reborn as a normal and kind human being again and again... ;-) ok, jokes aside, i think you get the idea, good and bad kammas don't get mixed up or cancel each other out. If it worked like that, the great Venerable Moggallana wouldn't have to suffer his ghastly death under the hands of a bunch of bandits even after he had attained Arahantship. For one who does some very wholesome kamma while also commits some grave one at the same time, the future rewards and punishments will be just as proportional. In the case of Alice, since she doesn't kill, that'd eliminate any potentially horrific kamma in the future. All she needs to do is to try to cultivate only wholesome kamma and she'll reap the corresponded wholesome future rebirths. And if going even beyond wholesome worldly kamma, she also cultivates supramundane kamma (ie. practice 4 Noble Truths, 8-fold Noble Path, perfecting Sila/Samadhi/Panna, etc.), she could eventually get that ultimate supreme reward: Nibbana. And that's the real beauty of the Buddha's Teaching, it's available to anyone willing to cultivate it regardless of caste, social status, gender, age, intelligence, etc...

Having lived, living, like a real powerful and wealthy being, put goodwill, compassion, appreciation and equanimity toward all being into action, not only does such live the Brahma-life (holly/sublime life) here but will reappear in the Realm of the Brahmas. Also such is gained right here, nowhere else, so don't one miss out a seldom chance, now as you got such a powerful position.

"We’re not in this to compete. We’re here because each of us has a disease inside, the disease of craving and ignorance that causes us to cause suffering. We’re here to treat that disease, but at the same time we want to make sure that our treatment doesn’t have a bad effect on other people."

~ Thanissaro Bhikkhu "The Implications of Goodwill" https://www.dhammatalks.org/Archive/Writings/CrossIndexed/Published/Shorttalks/171011(short)_The_Implications_of_Goodwill.pdf