How would I know if a single mum was dating someone without speaking to her?

I basically know this single mum, but not personally because I have never spoken to her, but I would like to get to know her, but how do I know that she isn't dating someone else?? All I know is that she is a single mum, but I haven't a clue as to whether she is dating someone or not! I don't want to look like an idiot by asking her out and then she says "No Sorry i'm already seeing someone" That's the last thing I want is to look lke a fool, but I am attracted to her and i haven't a cluw how she feels about me because we haven't even spoke, but we see each other once every week because we do a course together.