Heather starts out being able to hack novice terminals, and can eventually hack any terminal.
You gain affinity with her by gaining levels, having her hack terminals, consuming her custom made aid items, and completing her personal quests. This is great because she doesn’t have dislikes of specific actions you take, making her a much more flexible companion for any type of play through.
The intro text states “over 1200 lines of dialogue” for starters, which far exceeded anything else on the Nexus upon release. One look at the Nexus page for Heather and it’s clear that llamaRCA put the same commitment forth in making this mode as she did with Willow.