I've seen lots of cases of flirting between FAs and passengers. Even I've had an FA flirt with me on occasion - why, I'll never know. But I've never seen it taken even close to this far on the plane. I've always found the FAs to be very descreet about their flirting and to not let in interfere with their work, which I think is fine. If it interferes with their work and effects negatively other passengers, then it's totally out of line. If the passenger giving/receiving the flirting gets some special treatment though, it doesn't bother me at all.