Why would this woman keeps full-on staring at me & not smile or look away then act reserved and silent around me but talkative with other people?

Anonymous
I have known her for five years and through those years she would stare at me every time she sees me (which is like 3/4 times a week) even if I’m talking to someone or focusing on my work and I’d look up or to the side and she’d be there full on staring at me from a distance (even through the window on two occasions) and would maintain eye contact with me until I look away and doesn’t even smile or blink.
I’ve also had other people coming up to me & mentioning her staring at me without my awareness & found it strange. I’d also catch her giving me side glances through my peripheral vision which I find weird and she would do this when she’s ignoring me and talking to other people.

Besides from her stares, I find it frustrating that she would act hot and cold nearly every week that I have to be around her. She acts more cold towards me if I’m being too nice to her such as helping her out or doing other things for her compared to others even my closest friends whom she’s more talkative and outgoing with. It’s just with me, she gets all silent and tried to end the conversation quickly. But every now and then she would make small talks or jokes with me if she’s in a good mood.

However, I also need to mention that there’s 2/3 occasions where she would make direct comments about relationship and sex at me in-front of other people such as my friends and smirks at me which I’m not sure if she’s joking or being serious since I’ve also caught her staring at my chest and butt before and she makes it well known that’s she staring at it.
She also doesn’t seems to care about invading my space and would caught me off guard with it like on one occasion, I was sitting down with my friends and she came to stand in front of me somehow she managed to have one of her leg in between my legs. So I’m really confused as to why would she act like this or why would a female acts like this towards another female?
Why would this woman keeps full-on staring at me & not smile or look away then act reserved and silent around me but talkative with other people?
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