Help or advice and stuff about why she is acting this way now?

one of my best friends since we were like in grade5 is dating the wrong people i think? or maybe its her acting this way or maybe they are tricking her in some way to act a certain way? so we are in high school a few years she was the same as before for most of it until she changed at the end or mid way or last year.. she started to date some older guys since they asked her out and she was happy she got attention from more guys she said but they only dated her like a month each or so and this summer she was sort of sad and said that after a few weeks or so of dating they wanted to have with her and said they liked her but had to have it for the relationship to grow but then they broke up with her after she let them in bed a bunch of times. so anyways she changed sor tof but she still dates older guys but has been wit her new b/f over 2months but ti sounds like he is doing the same thing the other guys did? but she cant fully see it since its sort of different i think? she admitted he often wants with her and she said last week she thought she was pregnant and i dunno shes just getitng out of control adns tuff i dont wnat her to have a baby and have to drop out of school? im not sure what to say to her because she might get mad and not tlak to me anymore and she will end up getting hurt and shes my longtime friend so i dont wnat that to happen soo what can i do or say to her??