Alright, I talked to her today. I was thinking about the spot on the bench idea, but I saw her doing front squats yesterday, and I thought maybe I'll just ask her to show me proper form on those. So after she finished a set up pull-ups, I walked up to her to ask her. Everything about her body language said "go away", she took one ear phone out, and she sharply said, "What?". But I asked anyways because I had to at that point. She was polite and gave me some pointers, and then I left, thinking "oh well...that was completely opposite of the smiles I got the other day".
Fast forward about twenty minutes later, she walks up to me and asks how the front squats went. I tell her about it, and then she apologizes for her demeanor earlier, and said she was frustrated then because she wanted to jump back up and get one more pull-up right when I approached her. We talked for a few moments, she was extremely friendly and smiling again, and then I finished up my workout.
I forgot to ask her her name, so I'll have to try to do that tomorrow. But overall, I feel really good about the interaction, and am glad I talked to her. I can't say if there's any interest on her part, but it was nice to do a cold approach after not having done any for so long.