Amanda Knox, who was reconvicted last week of the murder of the British student Meredith Kercher, has told the Guardian she feels "stranded" and "trapped".

Knox, 26, spent four years in jail with her former Italian boyfriend, Raffaele Sollecito. The pair were arrested in 2007 and convicted in 2009. Rudy Guede, a local drifter and known criminal with a history of break-ins, was also convicted in a separate "fast-track" trial. He is still in prison, his sentence having been reduced from 30 years to 16 after he implicated Knox and Sollecito. He could be released in two years.

In 2011, Knox and Sollecito had their convictions quashed. But Italy's supreme court ordered a retrial, and last week a court in Florence found them guilty, sentencing Knox and Sollecito to 28-and-a-half years and 25 years respectively.

Knox has this week returned to the University of Washington, where she is studying for a degree in creative writing. The university and fellow students have been supportive, but in an interview with the Guardian, Knox said she felt desperate.

"The stance my university has taken is no matter what is going on with me legally I am still a student, and I've been shown support as far as security goes. I haven't had any backlash. If anything people have been quiet and respectful, but it is like I've just been diagnosed with cancer."

Last week, before the verdict, she had said she felt branded, but now she said it was on an entirely new level. "There's nowhere I can go where there's not this knowledge that I'm this girl who is convicted again. And it's so invasive on my life on a fundamental level.

"I'm never going to be OK with the idea that somebody can quote some judge's decision and say I'm a convicted murderer. I'm still processing it. Being marked as an exoneree is one thing, but being marked as a criminal is another thing and it hurts. It's not OK. I'm not OK with it. It makes me feel so much more isolated and branded."

Knox said the situation was worse for Sollecito, who is in immediate danger of being sent back to prison. "This was a devastating blow for both of us. But he is right in the middle of it. There is no escaping for him." She had spoken to Sollecito since the verdict, and that he sounded broken. "He's really determined, trying to be strong, but I can hear in his voice he's not OK." Asked if Sollecito was angry with her for being in the US while he was in Italy, she said: "No, this is my home and he knows that. He's not angry with me at all." Knox and Sollecito will appeal again against the verdict – the final chance to clear their name.

In interviews with police, Knox confessed to being at the scene of the murder and wrongly identified Patrick Lumumba, a bar owner, as the killer. Within hours she recanted the confession, later claiming it was made under stress and extreme exhaustion and she was beaten in prison.

The Florence court has not yet given its reasons for reinstating the convictions, and does not have to do so for up to 90 days after the verdict. But last week the lawyer for the Kercher family, Francesco Maresca, described the verdict as "justice for Meredith and the family".

• The full version of this interview will be published on the Guardian website on Saturday 8 February. © Guardian News and Media 2014