Girl blushes mid conversation?

Has anyone ever noticed this? Today I girl I have a crush on (I think she has a crush on me too maybe) Anyways, I asked her to help me in my cubicle and she was showing me something on my computer. Five minutes into our conversation I look over at her and her face is red, like she's blushing? Mid conversation? Why?

Again, I pick up on these things, but yesterday I was talking to this cutie at work, I was kind of teasing her, but not really? She was a talking to me in my cube and she turned the corner and stuck her head back around and she was blushing big time? what is a mid convo blush?
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Girl blushes mid conversation?
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