Pregnancy possibility?

My friend is 14 (so am I) and her boyfriend is almost 17 and they've had sex six times, all without protection. I'm very worried about her because her period was due July 24 and it's July 29 and still no period. She insists she's ready for a baby but I know for a fact she's not because she is definitely not responsible enough and her family doesn't have a ton of money. Her dad could also kick her out if he found out. I'm worried she's pregnant, what do you guys think? She's had some of the symptoms but my mom thinks they're all in her head. How do you tell if you're pregnant?