i wouldnt reccommend Depo. I had it for two year, and it took me another two full years after stopping it to get back to a propper cycle with periods etc. i dont think in someone so young it is a good option. i don't think any contraception which stops them from having a regular cycle is not a good thing, just my opinion, I know I wouldnt like it if it was my daughter, at that age, i think the pill would be best if there is no chance they are going to refrain from being secually active.

i am not judging at all, just a query, you said you don't think she is responsible enough to take the pill, perhaps this means she is not responsible enough to be having a sexual relationship, perhaps she needs a little more guidance in that area? just a thought?