Cycle buds

Natalya

So about 4 months again I made a friend. We work together, hang together everyday. Since then our period of been thrown off. Now we both get our periods at the same time of month, same day, except mines only 4 days and hers is 7 days. Anyone else have this too? With a girl friend if theirs? This has been like this for 2 months and month before that ours was a week apart.