That was a buggy issue in the vanilla version of the game. The Co8 mod basically disabled this feature, so that any NPC's inventory is freely accessible.
IIRC, get your PC leader/husband to talk to Melany while she is joined as an active NPC, and there is a dialogue option that tells her to stop picking things up and to share with the group. I think there is a similar dialogue option for Pischella the mage. However, this option might be bugged, so I am not sure it works.
Another way is to have Melany cast the Goodberry spell about 30 times. Then fill up her inventory with goodberries, so that there are no open slots. Now she will still auto-loot a share of the treasure, but at least she can't pick up any more items. You can do a similar thing by having a mage scribe 30 inexpensive lvl 0 scrolls, or using arrows bought from a merchant.
If you have a good thief, try kicking Melany from the group, then picking her pockets. Make sure to save first, because she will turn hostile once the inevitable fail happens. Afaik, you can grab anything out of her inventory that is not being worn this way. You can steal all sorts of stuff from other NPCs this way too, especially from Rufus/Burne.
If that doesn't work, getting Melany killed should do the trick. Once an NPC is dead, you can loot their body of whatever equipment you want. Then go back to Homlett and resurrect the NPC by talking to Jaroo or Turgon. While early on this is a very expensive solution, later in the game you can generate as much cash as you need by forging/scribing high level magic items and selling them. Ressurection costs go up for higher-level NPCs, so if there is something you want to get out of Melany's inventory early on, best to do it while she is lvl 1.
A fourth possibility, and I am not sure if this works, would be once you have a mage high enough level to cast the Dominate spell, you could kick Melany from the party, then cast Dominate on her. I think that will allow you to freely access her inventory. It will likely turn her permanently hostile to the party once the spell wears off, though. However, I've done some weird stuff like charming a hostile Otis into the party, then travelling back and forth between Homlett and Nulb till the spell wears off. Otis auto-returns to Nulb, turns friendly and forgets he ever met you, thus allowing you to invite him to join again.
Post edited July 02, 2016 by Dreamteam67