There’s a chance it’s not her period and it’s implantation bleeding. If the bleeding turns out to just be spotting, she should take a test around the time she would have expected her period normally. The first time I got pregnant, I thought I started my period a couple days early, but it was just spotting and I got a positive test a few days later.

No. A one off weird cycle is normal.and happens to us all. It doesn't mean they need to go to a fertility specialist.

That seems normal, cycles change from time to time. Sometimes people ovulate at different times in their cycle, and sometimes period comes earlier or later. Nothing to be too concerned of.