Nah, just the "glimpse" scene into her past that's available after you complete a faction or main questline and she's been dismissed. It's a little, abstract memory that gives some insight into her character but because of who Eris is, there was never any plans for quests for her.
Unfortunately, your guess is as good as mine for the sneaking thing. I don't remember it ever happening on my end with a vanilla install but it does happen to some people every now and then. My guess is something funky is happening with her AI, although it never happened with any of the other followers.
The summon spell or disable/enable trick to reset her is the best workaround.