Is anyone's AF in sync with a friends?!

So I have a client I spend 16 hours with a week and I think because we are always together that our period started to get closer together. It's been like this for months now. Mine always comes first and hers will follow a few days to a week after mine, but she got hers today. Hard to tell if she's early or what because my prior never comes the same time. I am on cycle day 24 and I have been having BFNs.