I used to have a girlfriend like you, then I took a Dawnguard to the Social Life.
(arrow-to-the-knee jokes are dead aren't they? Ah well, I'll get over it.)
I've had no official problems with Dawnguard, but two minor annoyances I've find with my mods were as follows (I'm putting them in spoilers just because people tend to be edgy about this sort of thing

)
Spoiler
Immersive Skyrim Thunder became EXTREMELY annoying in Soul Cairn, where there it constantly plays its loud and rolling thunder SFX. Couldn't even hear most dialogue through it. Not a conflict, I don't think, the weather in the cairn just happened to trigger as thunder the whole bloody time.
Also, you may want to lose whatever map replacer you use, as there are new areas that are off the border of the old map.
Otherwise, everything's working out well, and I'm slowly seeding more mods into my Load Order again to continue testing. Happy hunting!