I’m confused with this girl, what does it mean?

I have worked with this girl for the last 3 months and she has always acknowledged me and made sure we have eye contact and she smiles. I’ve started talking to her a few times and now seems like she ignores me. Although when I notice her looking at me from a distance sometimes she waits for me to look and she smiles.
That’s why I’m confused because for example this could be with in an hour, we walk past each other I look at her and she ignores me then later I see her looking at me and when I look up at her she smiles. It’s frustrating because I don’t know what it means her ignoring me makes me feel like she’s not interested but when I see her looking at me with a smile I’m thinking why is she sudddenly being friendly and looking at me?

I’m confused with this girl, what does it mean?
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