Any girl that chooses to have sex is well aware of the possibility of getting pregnant. Especially if they don't use protection. Sometimes pregnancy is possible even if you are using protection. So what happens when it fails? You have options: keep the baby, have an abortion, or give it up for adoption. The point is you shouldn't do what people tell you to do if they were you. You should ultimately do what's best for the baby and yourself. No one really knows the specifics of your life, or what got you into this situation in the first place.
So, all I can really say to girls in this situation is: Think about it. Research your options. What if you were that baby? What would you want your mom to do? And above all: Don't let yourself get pushed into doing something that you will regret for the rest of your life.