I work in an office that is located on two different floors in the building. My co-worker (who appears to dislike me) and I do not work on the same floor. So I don't know why she goes out of her way to use my computer, let alone use anyone's computer at all, since she obviously has her own desk/computer. Normally, this wouldn't bother me. But the thing is that she always ignores me when I say "good morning." And if we're on the elevator, she looks into mid-air or doodles on her cellphone. This has been happening a lot BEFORE I suddenly noticed that she's been sitting at my desk. I discovered this once I noticed that her first initial and last name was on the log-in screen. But due to her unsettling demeanor, I never questioned her about this, as she basically treats me like a panhandler/as if I have cooties. Although, one day she forgot to log-off on my computer. So when I arrived that morning and logged in, I apparently kicked her off her computer. So it was then that she admitted that she's been using my computer, and therefore needs to use it to log back on and off so she can use her computer. I kindly accepted, to which she said thank you when she sat at my desk. But after that, she was still (and currently) her usual unfriendly self. So basically, that day was the ONLY time she actually spoke to me. Other than that, I feel invisible to her.

FYI - Initially, I noticed her first initial and last name on my computer only on Monday mornings. But now, I notice it every other say or so. So she's basically gone from using my computer on the weekends to more frequently. How do I handle this?