My girlfriend and I go through the same thing. The only difference is that we are both extroverted and dominant personalities. So when we get heated it really gets heated!! I do have a lot of your qualities though and extremely enjoy my time on the computer and being alone (even if its just hanging out and reading).
I use to think she was manipulative but I found she actually just would rather hang out with me (go figure) than anything else.
I think your lady just really likes you and would prefer to spend time with you over anything else!
Just let her know that you need your alone time and I'm sure she'll try to oblige
