How can I get Lydia out of my house?
Lydia's your housecarl (bodyguard), and lives in Breezehome. Outside of possible console solutions, there's really only two ways to get her to move elsewhere:
- Recruit her into the Blades; my understanding is that she'll then make Blades HQ her home when she's not following you.
- Marry her and move into another house you own. Not really an option for you at this point, however, as you're already married.
Your only other option, I think, is to simply accept that you and your wife have a live-in bodyguard thanks to your position as Thane of Whiterun. It's not really anything for the wifey to get upset about -- Lydia even has her own separate bedroom! In fact, having a housecarl is definitely a sign of honor and privilege, so your wife should be rather pleased with the situation!
Another option is to recruit her as your follower once more and head out to the nearest dungeon so you can practice your fireballs. Accidents do happen...