Hmmmm, if you have 2 followers she won't come with you, but that dialogue usually triggers after you have asked her to join and she accepts, then rejects you becasue you already have 2 followers. What you have sounds different to this.
At least try out the dialogue options you have tried before, they are usually grey'd out but they sometimes lead to a new dialogue option which wasn't there before, I think this is what I did. You might have tried this already and if so I'm not sure what else to suggest I'm afraid......
She and I had a falling out during her quest, I had to put her down (Im in hardcoe mode - balistic fist made it pretty instant and pain free) but next time I loaded up it said she was back at the outpost! I checked and she wasn't there so that was just another minor bug I spose. I couldn't complete Veronica's quest becasue she became all non responsive, Arcade is looking good though, him and Boone both have combat armor and look like a nice couple and all 3 of us seem to be getting on nicely right now