It's sort of tangential, but I don't think she could if the DA wanted her to testify. Fifth amendment protects you from incriminating yourself not from being subpoenaed as a witness. I'm guessing that if she decides to change the story on the stand or lead the jury to believe that she filed a false police report, she can be charged with a crime herself. I think DAs usually drop cases when victims choose not to press charges because building the case without them is hard. At this point, I doubt that would be the case as quite a bit of evidence is easily available to them, including pictures of any bruising that might've been there, the police report and other subsequent interviews conveying the story. At this point, I don't know how much Varlamov would gain from buying her silence assuming he even could - although it may very well be the case that the DA's ability to prosecute will be substantially hurt if she becomes far less cooperative. Honestly, I'm not so sure how strong a case they will be able to build unless there is clear evidence of bruising consistent with the story at which point, I'm not sure why she'd want to not testify as she would win a civil settlement anyways and she's been pretty clear that she wants him behind bars.
As I said, I'm not a lawyer, so all this is based on a very limited understanding of how these things work.
