Girls, is my stepdaughter flirting with me?

My 18 year old step daughter seems very flirtatious when she's around me alone. She often stands or sits very close to me, so I can feel her chest on my body. She looks me right in the eyes when she does it and stares longer than normal. I can't figure out her intentions, if any, or what she is up to?
Any of you girls with step fathers know about this? What would be the right thing to do?
Girls, is my stepdaughter flirting with me?
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