Although does it stop with her having an interest or does it go further...and if it does how to do that
DLC with a bunch of blue haired elves.
Yeah there isn't much to it, just a chance for corruption and affection points with some of the companions. And if you save Ursula an orc chief in Act 3 will comment on it. That's it. As for your second question only your party members should be affected.
For Harbor Master Part 2 the bandit cave is two zones "East" of Cinkahn. Redknight made an error in their walkthrough for that quest. Go east from the tavern, and you'll get to the east gate of Cinkahn, go through the zone, go past two blue bird monsters in the next zone, keep going east, and exit. Then you'll get to the zone with the cave, and some sexually active plants that Meredith takes an interest in. Just note the cave is a little buggy, you can complete the quest, but it's possible to get stuck in a loop if you're not paying attention to entrances, exits, and doors.
You can't kill everybody. But you don't have to accept companions, and you can kill some of them. The game also allows an evil path where you become a tyrant over the world essentially in the epilogue. Instead of saving the world leaders at the end of Act 3, you get to kill them off, to establish yourself. So a lot of important npcs you meet during the game can be killed in the ending.
You can try redownloading the game if possible. That can happen on older pcs with low specs, and if the game files got corrupted when being unpacked. I have never had the issue, so I don't know if there are other workarounds. If the redownloading doesn't work, let me know, and I'll try and come up with something else.