I completed the Heartache by the Number quest by letting the NCR handle the van Graffs and
Alice of the Crimson Caravan. After that I started a quest by working for the van Graffs. Now they
want to kill Cass, which of course I can't allow. So I killed them all, but Cass was kind of pissed
at me for not informing her. I did tell her the van Graffs wanted to meet her, but other than that,
there was no way for me to inform her.

So after I cleared out the Gold Rush (think that's what the store is called?) she got a little pissed
with me but after that wanted to take out Alice of Crimson Caravan as well. I've got a little bit of
a dilemma here;

I promised Jackson I would let NCR take care of Alice, and I always stick to my word. But I'd
also like to do the favor to Cass (I know about the extra perk). I'd rather help Cass than the NCR
but that'd mean I'd have to break my word with Jackson of the NCR. I've never broken my word
so I don't really know what to do. For RPGing sake, what would you guys do?

Well, the Van Graffs genuinely had it coming, being a bunch of murderous thugs and all. McLafferty seems to be more of a white collar criminal - and an old woman, to boot. Just wouldn't seem right subjecting her to a violent death. Then, of course, there's your promise to Ranger Jackson.

Ideal solution would be to just talk Cass out of it. Not sure if the game will allow you to (possibly for lack of dialogue options in unexpected situations). If not, then you can just imagine that you did and move on. That's what I'd do at any rate - if the in-game options aren't exhaustive enough for me, I just fill in the blanks for myself.

Thanks, sounds like a plan

The VGs asked to see Cass, so I took her to them. I didn't let them shoot her though, we decided to battle it out. 10 Stealthboys and an All-American later me and Cass walked out of there with the contents of the store. She was happy, I was happy, not sure about the NCR.