Attracting Someone On Twitter?

I've recently got to know someone on Twitter who is ten years older than me. Initially I was just chatting to be friendly but I've started to become attracted to her, but I'm inexperienced with dating older women so I feel more worried about making mistakes with her. I actually feel like I've done okay with the talking so far though. Anyway, just as I thought it was going well, she's started what looks like flirting with someone who seems popular with a lot more followers, but also ten years younger. He is reciprocating and I think it would come across as desperate and too early to call her out on it. She's obviously doing it out in the open which is a bit of a low blow, I feel like I could be overreacting but at the same time I'm cautious of overlooking obvious signs they're flirting and missing out altogether. What would you guys say would be the best way to proceed?