Been away for a bit. Last time I kept reading if anyone told Serenna to leave, the game becomes bugged and then you can't continue on anymore. I started playing again and have Serenna following me. I would like to be alone but I am afraid to tell her I no longer need her anymore. If I tell her to leave, will the game be bugged?

If I tell her to just stay and then she leaves on her own, will the game be bugged?

I don't know what to do. I find I rely on her to much since she can't die so she kills my enimies for me, hence making the game a bit easier. I would also for roleplaying wise, like to adventure alone for now.

So what can I do, that will not bug up the game? Should I just continue doing the Dawnguard quests (playing as a vampire) and then Serenna will leave eventually by script? Or can I tell her to leave or wait and not bug up the game?

Just save the game, make her leave, then try to ask her to come back/see if the option is still there.
If you can't get her back, then load.

I havn't had the problem where she can't come back, but with no Patch for all the Bugs in Dawnguard, anything can happen.
Hopefully, they'll make a massive patch for all the DLC's and Vanilla game soon.

If you are on PC there is a console command to get her back if you get the dismissal/wait bug.

Huh?
You mean... you're not using the Unofficial Dawnguard Patch?
It's fantastic - I wouldn't play without it.
I have pretty well completed all of Dawnguard (44 hours).
Guess what? No bugs.
Very enjoyable, actually...

I forgot to say, I am on the xbox. So no unoffical patches for me.

Thanks guys for your help, I will do as you suggest Samm and see what happens.

I've got Skyrim in the 360, so no patches for me I'm afraid.

Sorry, can't help

apparently it's also dependent on where you go with her.

There are some places she won't leave, or will wander away on her own, and when dismissed never comes back. That's based off of a combination of several threads I've read around here.

from my experience, i could no longer re-recruit her upon entering Volkihar Undercroft the second time. probably should stay away from there

and also, don't enter dimhollow crypt ever once you've rescued her - she will be invincible like http://www.youtube.com/watch?v=Aym1Hc2_58k. it caused my game to CTD whenever she got involved in a fight after that

weird, it just goes right through her. So her clipping is turned off by doing that I suppose.