Tricity bus experience

I don't usually travel by bus; it's been a couple of years since I last traveled on a CTU bus. Today, I had to go from Santemajra (near Kharar) to ISBT 17. The bus stop is near my place, so I thought, why not? Well, the bus was 15 minutes later than the app predicted (not that I really cared), but when I was boarding, I tried to enter through the front door. The driver told me to go back, so I did—and then he just drove away. I barely made it in, and, man, it was crowded. When I finally got a seat, the girl sitting next to me suddenly threw up. I was listening to music, so I just paused it and didn’t react much. I was thinking about my next move, but then the bus halted at ISBT 43, and she got off. Now, my question is: what should I have done? I only had a couple of seconds at most. I was about to remove my earbuds, but she left. Though, I think she was supposed to get off at ISBT 17 too.