Partly her parents, for refusing to allow her to go on birth control as a preventative in advance. She did ask. Back then, in my country, parental approval was required by law for people under a certain age. That has since changed.
Unfortunately it took a lot more than asking (i.e. it took "a pregnancy") before they took her seriously.
Actually i think it’s mostly the parents fault. Sure you physically played a part but teens in general are dumb. That’s just how most teens act…no shame in that. Very little impulse control and lots of hormones.
A parents job is to TEACH their child how to navigate the world safely, and that includes how to not have an unwanted pregnancy. One can encourage abstinence, but it’s also important to realize that kids are not property. They will do what they want, and only follow abstinence if they want to. If you child refuses to follow your advice, at least help them practice safe sex. Safe sex is better than unsafe sex.
Unfortunately it took a lot more than asking (i.e. it took "a pregnancy") before they took her seriously.
But primarily, yes, my fault and her fault.