Period or implantation bleeding ?

My cousin had implantation bleeding or she believes it was implantation bleeding that lasted 6 days like a normal cycle. Has anyone else experienced this. She pretty much thought it was her period. She recently had her baby and he’s nice and healthy. But she had no idea she was pregnant the 2 months. Because she got her cycle like normal. Bleeding for 6 days. I wanna know if there are others out there that experienced this