New way to meet people

The el train was full of commuters leaving downtown at the end of the workday. At one platform, a young woman got on; her petite build and short haircut reminded me of Tinker Bell. She seemed tired in some distinctive way. She wasn't winded from running… no, she looked the way I feel when I think I'm going to throw up. She looked like she was going to pass out, and a woman gave up her seat for her. After a minute, the seated Tinker Bell leaned forward and retched an orange mess that splattered directly between her feet. Another woman helped clean her face with tissues.

A passenger notified the train operator; he stopped at the next platform and came back to confirm that the woman was not having a medical emergency; he sprinkled sawdust over the orange puddle and the ride continued.

I was a little surprised to have seen it coming. I had an empty plastic bag in my backpack at the time, and I could've offered it to her preemptively. I'm just not sure of the most tactful way to offer it: "Excuse me young lady, you look like you're about to vomit. Would you accept this bag? Please forgive me if that's your normal expression."