Is she trying to tease me?

Hello and thank you for reading and perhaps giving advice.

There's a girl a know since childhood, we were always close since then and it's a nice and (from my side at least) platonic friendship.
We even call each other brother and sister. I'm 20 and she's 19.

So the other day when I was at her place helping her with school-related stuff, I watched a movie lying on her bed while she sat at her desk next to the bed doing exercises. She wore a short jumper-like dress and slightly transparent pantihose underneath. I thought her to be somehow overdressed because she usually wore simple things when I come over. Used to see each other in casual wear, you know.

I would turn and answer her questions if she encountered problems with her exercises. Once she asked I couldn't help but notice her dress was sitting in a way which left her legs way too exposed, to the extent I could see her crotch. But I thought maybe she sat cross-legged for a while which maybe caused the dress to be like it was then. Also, she wore the pantihose so not really that big of a deal. When she was finished I got tired of the movie (twilight saga: eclipse...) and she suggested that we watch a sitcom, I said sure and she crawled over the bed to the PC (which is reachable from the bed) and using it, (accidentially?) gave me a view of her bottom (in pantihose still) because the dress was still sitting a little too high. Her position was also like, bending over, you know.

I don't desire any relationship or sexual interactions with her, so I just looked away until she sat next to me on the bed.
After a while she said it would be too hot and got rid of the pantihose, I of course looked away as she did. Her dress still exposed so much that I could see her friggen thong. I told her, half jokingly, but she said it would be okay as I'm her brother. (Wouldn't you just pull your dress down a bit regardless of who it is??)
When it got late, she offered me to sleep over. We slept over at each other's places before a lot, so still normal. This time however, she said her parents had an argument and her Dad would occupy the couch in the living room - but I could sleep with her in her bed.
Under normal circumstances I perhaps would, but given that stuff she did before, I lied to her that my Dad would need me tomorrow morning so I had an excuse for going home. And I did.

Now I'm not sure if all that "flashing" (to say it bluntly) was intended, or if she was just being comfortable around me (what she usually is, but not the extent of showing me her thong-clad nether regions).
I don't want our friendship to be threatened by her wanting something, but I'm also afraid of approaching her about that topic because if it was all just nothing, she would maybe think that in fact I wanted something because I thought she wanted... and so on. Basically, I don't want to start the conversation because if I'm wrong it might be one hell of an awkward moment.

Please help me. What the hell is going on in her mind??
Thanks in advance,
Sean89

No need for any conversation about it unless she actually makes a move. Rejecting someone when they haven't even gone for you would be presumptuous and insulting. Just keep avoiding situations where she might be trying to take it further.