Can married women have crushes on people?

I just noticed just now. There's a married woman in my apartment who always looks at me when I always walk past her or getting the mail. She's the only person in my apartment building who would look at me. I'm not sure if this behavior is normal or not. There is no awkwardness, but she did act mean or rude one time when I was helping keep the elevator door open for her. Is it normal for married women to have crushes on people outside of their marriage?
Can married women have crushes on people?
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