Flirting

Is lingering physical contact a sign of interest?

I've noticed this happen with my crush on numerous occasions.

1) Showing her my notes on my iPad, she stood so close that her arm was pressed into mine.

2) We both went to a part of the whiteboard where the professor wrote something on the board. She was walking behind me, and stopped while standing so close her arm was once again, pressed into mine.

3) Sitting next to each other in lecture, and our elbows made physical contact, but neither of us acknowledged it nor moved away. It lasted for at least 45 minutes.

4) This happened twice in 2 days. Sitting next to each other, and when showing something on my laptop, her arm was pressed into me, without acknowledgement nor moved away.

I know this may seem like a tupid question, but I need insight on how significant signs like this are.

Updates
+1 y
Thanks for the responses.

I've forgotten two more thing sthat have happened.

1) lingering hand on my arm, sometimes while looking at me

And

2) her knee was touching my leg and she didn't move it away, until she had to leave

I would happily make a move, BUT, she has a boyfriend

[She never talks about him, except for the rare slip up if she's speaking to one of her friends, she tried to correct herself the first time by saying her friend]

So... yeah, I don't know how to conduct myself
Is lingering physical contact a sign of interest?
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