Why does the woman I like leave everytime other people approach me to talk?

1) She knows about my feelings but she still is in a relationship about to end.

2) We work together in the same company

2) Yesterday, during the break, we were conversating. Suddenly, an old co-worker approached me and just asked me how am I.. I turned to him and I told him ''I'm ok, thanks'', and when I turned again towards her, she had left without saying a single word. Even the other person told her ''hey, what's going on?'', but she didn't reply.

Later on, I talked again to her and she seemed ok, like nothing had ever happened.

What does that mean?

Why does the woman I like leave everytime other people approach me to talk?
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