Your GF has high risk HPV. These are certain strains of it - her doctor will be able to tell her which one she has. It doesn't matter much here, except that these are strains that affect the cervix. HPV is a genital infection, meaning it can affect the entire genital area. Just because she may have been infected through skin on her vulva, for example, it doesn't mean that the high risk strain won't affect her cervix.
It's important that she gets the cryotherapy. She has abnormal cells on her cervix which could lead to cancer if she doesn't.
Condoms reduce the risk significantly, but not entirely - https://www.nejm.org/doi/full/10.1056/NEJMoa053284
Now, did you give it to her or did her ex? Who knows? You'll never know, and does it really matter? Do you give her oral? It's possible, though not as likely, that you could have it in your throat and transmit it to her orally.
How long prior to you was she last with her husband?
She could have had this prior to your relationship, you could have had it prior to the relationship, or maybe you both did. It's estimated now that about 90% will get HPV in their lifetimes at least once. Don't worry about who gave it to her. Just support her.
Here's some info on cryotherapy that you can read so you know what to expect when she goes through it - https://www.plannedparenthood.org/learn/cancer/cervical-cancer/what-cryotherapy