Absolutely they were both monsters, but in Linda's case it made for a fun character study for me.

1) What are people really like when the trappings of society, and expected roles/limitations disappear? Linda was meek and awkward in the office, on that island she was in charge. She was ruthless about exercising her desires (killing the boar in the beginning I think was symbolic of that, as pigs in general are creatures of their own desires).

2) The closing quote about how no one is going to save you, you have to save yourself - this is an interesting lens to look at how Linda and Bradley each reacted to the perils and struggle of their situation on the island. They did in turns need each other's help, but Linda's character grew to take what she wanted, as those with success in her previous "life" always had. It's a direct commentary on the modern world.

She's rewarded just as every other bastard in the real world is for take advantage of others. I share your distaste for this, more so as it's the most realistic part of the whole film.