Eh, I'm bored so I'll answer the OOC.
I would think it was fairly obvious Rel had no intention of attacking the party; she's a profit motivated person and said as much to Kili ("my chances of getting paid are nil"). She wouldn't get anything out of attacking the others and is smart enough to know her chances of ambushing five or so warriors and surviving are considerably slimmer than her chances of slipping past the enemies in the catacombs and merely starting over somewhere else, not to mention that the party isn't carrying much and if she did win somehow the only things of any value would be Tal's weapons and maybe Eon's amulet. The risk greatly outweighs the reward, and she's not greedy enough to kill someone over their possessions anyway. Especially in such a dangerous situation like this, where if the 0.003% chance came up and she killed everyone and took their stuff, she'd still have to get past the undead and outrun the Orcs. To summarize: in character she'd have to be a damn idiot to attack the party, and Kili really should know that; out of character, I'm not a confrontational person and I hate fighting other players, so I wouldn't take a shot anyway.
Also, I know Draignean well enough to know he takes his characters fairly seriously, and it's canon that Magnus wants to kill Rel (he's said she 'owes him a duel' and it would be 'a fair fight to the death.' He has twice as much HP as I, and +2 to hit/dodge when fighting a single opponent, and a sword that hits for three times as much HP as I can regen, so unless he got unlucky every single round of the fight there is no way that duel wouldn't end in my death). The only hope I would have of dodging that bullet would be to avoid the party long enough for both Kili and Magnus to get offed and then rejoin the rest, which frankly isn't worth the annoyance and effort of making the GM juggle the main party and then me doing whatever I wanted elsewhere until that happened, and even then frankly Rel has no reason to join up with them. She has no opinion of Justarr or Atriard and dislikes Kili (argumentative), Magnus (sexist pig), and Kir'zhon (death threats and general racism Dunmer have for Argonians), and since the main plot hook hadn't been introduced by the time of her leaving she would neither believe nor care about anything any of them had to say, assuming they even ever ran into her again. That wouldn't be likely; if Cyrodiil -which she has no stake in beyond robbing it- is currently a warzone, she would certainly leave the country for safer regions to burgle.
@ninja adwarf: Sorry dude. Like I said, I have no intention of rejoining the party again. One, possibly two characters want to kill mine, and it makes no sense for her to rejoin the party, now that she's left it, unless something major happened in chapter 5 that forced her to. That's a long way off though, and I don't want to hold everyone else up by making you divide your attention between a party that's actually doing stuff relevant to the plot while I mess around marking time until then. Just chuck her into a trap or something; at least that way her death will be useful so the rest of the party doesn't have to worry about springing it.
I might rejoin later but right now I just don't really feel up to it.