Your friend my dear is very normal. But her practice is not a normal one at this moment in time, where sexual intercourse could lead to many more challenges besides pregnancy, like Sexually Transmitted Infections (STIs) including HIV/AIDS.
Still though, having sex every day, many times does not guarantee a pregnancy. For a pregnancy to occur many factors come in play. For example she could be using a condom or other forms of contraception like pills before she has sex.
Secondly in young people, it is a common practice to portray themselvies as if they are very sexually active yet in actual sense they are not. She could be telling a lie to you so as to prove something.
Thirdly it could be chance that every time she has sexual intercourse it is not the time for fertilization to take place.
You need to know however that unprotected sex could lead to pregnancy among girls with functioning reproductive organs including you and your friend.
Young lady you are so concerned about your friend which may be a tempting situation for you to also try it.
Never use someone else’s experience to plan and live your life.Your life is yours alone and nobody will ever live it for you, but yourself will.
There are many reasons which could lead to her situation and one of them being that she is using a condom to protect herself.
She also may be having sex during the days when she is unlikely to become pregnant, but this may not be easy for you to learn and impliment because you are still young and growing up, so changes may come as you grow up,take it that your cycle has not stabilised.
There are many chances that at one moment that girl will become pregnant with an unwanted child and will stop going to school.
She may also get Sexually Transmitted Infections (STIs)which may ruin the rest of her life. Otherwise she is very normal but she has to live a more careful life.