Nesrail --
Glad you're still around -- I didn't expect a reply so soon! I do have some theories that I'm glad to share, but they're a little weaker with the information from your last post. Specifically, the cold-spots are throwing me off.
1) Do you (or your girlfriend) tend to lose a lot of small items? Put your keys on the table, turn around and they're gone?
2) What kinds of noises do you hear from the attic? Loud banging, or more of a tapping?
3) Do you tend to have bad luck in the house? Things are going great, but when you get home, your day goes bad on you?
4) Any strange smells? If so, are they good smells (flowers, perfume, etc.) or bad smells (rotten meat, feces, etc.)?
5) You mentioned birds -- how do they tend to act normally, and how do they act when something strange happens? Do they stay calm? Get excited? Are they excited in a good way ("Yay, food-time!"), or a bad way ("CAT!!! CAT!!!! RUN!!!")
I suspected before that it might be an unhappy house-wight, but I'll be honest and say I'm not 100% sure now. I don't know how many nursery rhymes you were told as a kid, but in Denmark they're sometimes called Kobolds or Nisse. They're spirits that live in a house, usually without anyone knowing they're even there, but if they don't like you (for absolutely any reason at all), they can cause trouble.
In pre-Christian times, land spirits (landvættir) of all kinds were venerated by Germanic and Scandinavian people, and the relationship a person had with their wights could drastically effect their lives for good or ill. In Germany, you get stories like "The Shoemaker and the Elves", but a similar pattern can be seen in a lot of family stories -- if you take care of your house-spirits, your house-spirits take care of you. They can be very temperamental, though; I suppose it's possible that this spirit could have been sleeping for a good long time, and your girlfriends' magick disturbed it. Maybe it doesn't like her particular brand of magick. Maybe it just doesn't enjoy her company as much as it enjoys yours. They're a lot like humans in their attitudes, some times. But, also like humans, they can be brought around and become good friends.
Others before me have suggested making a peace-offering. I would go one step further and offer it a bit of beer, a bit of food, and a dedicated corner in your house somewhere. Maybe in the attic, since it seems to like it there so much?
If you're dead-sure that this thing is no good, consider what others have said; that you might just have a negative spirit. These are also not unheard of in Scandinavian lore, but it has been my experience that a person can easily tell the difference between an angry house-spirit and a totally p*ssed off "other".
Either way, if you want to try to do real combat with this thing, there are a couple of simple things:
--- Iron: In Scandinavian lore, spirits (except Svartalfar and Ettin) hate iron. If you can get raw iron (like so-called "coffin-nails", or even just old-fashioned nails), and hammer them above the door frame (like over the bedroom door, etc.), that might help. Steel also works, but I find modern steel (especially modern steel nails) doesn't work nearly as well.
--- Rowan (Mountain-Ash) wood: This has long been known to drive away negative spirits. It is best to get some twigs with the berries still on them. Rowan is a small tree/large shrub that grows pretty well out there. The Danes were actually very fond of it, I'm told. Here is a picture of what it looks like:
http://www.mountainwoodlands.org/userfi ... wan-12.jpg
That should help get you started, anyway. I hope this helps, and I really hope that you're just got an angry house-spirit -- it would be much easier to deal with, in my opinion. I'll echo Cyberdemon in that I wish I could see it with my own eyes. It would certainly help with figuring out what's going on.
~ Runar
PS: If you need something more powerful, I have some warding and banishing spells from some Icelandic texts that might help. I hope it doesn't come to that, though.