[Philos]

I discovered that if you go to the Taylor (forgot his name) in Hommlett first and try to sell to him, he won't buy anything from the NPC except perhaps crossbows (IIRC). After this first "sell" attempt, you can remove ANYTHING in the NPC's backpack and add to your own PC backpacks. This doesn't solve the weight issue but as LP pointed out you fill her backpack with all kinds of light weight stuff so she won't pick up loot.