There are different contraceptives but I have never heard about the injection thing.
I don't know the country you are from as I think most of the contraceptive pills are peculiar to countries. But if you can find postinor 2 for your friend, it's a good one.
Also, using protection is likely one of the best preventive measures. (Condoms)
If she can actually insert IUD, then she is good to go. Intrauterine Device.
A toddler who won't stop crying!
I think the best contraception would be those that are natural. One of it is to make sure to not release any load when it's about to be released. I have heard many instances where those who have used hormonal pills and those that have used any hormone methods to prevent ovulation from occuring would have hormones altered. The problem is that, if used on a long term, it may prevent any future pregnancies. I think the best is to just use the plain old rubber as it is from my view the safest. Just get those which are thinner rubber to maximize the feeling.
Anyways, the other safe method is to make sure that it is within the safe range which could be calculated and usually is a few days within the last date of a period. Anywhere after the seventh day after that would be dangerous and it is actually also not easy for pregnancy to occur as it takes a lot of chances. I don't think taking hormonal injections and so on are good. Anything that disrupts the normal hormone cycle of a person would do great damage in the long run. The body's hormonal system if it goes haywired, would create chaos. Then that's the reason why there is belly fat especially on the belly part and it would accumulate on. Then some times, it is actually not a full proof method. Do read more on the topic and get some doctors recommendation to know more. But usually what I feel is the best is to just make sure to release load outside which isn't easy and takes a lot of control and practise in some ways.
I will not recommen injection for contraceptive. I will recommend the use of condoms
Meet a pharmacist.