Sandy Greenman met Steven Avery in prison after his conviction for Teresa Halbach's murder

Steven Avery's Companion Sandy Greenman on Their Relationship: 'It's Not Where it Was Before – There's Just Been Too Much Strain'

Being in a relationship with a man behind bars has taken its toll on Sandy Greenman.

Greenman, who met Making a Murderer subject Steven Avery in prison after he was convicted of Teresa Halbach’s murder, tells PEOPLE that their romance has cooled off for the time being, though they remain close friends.

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“We’ve had some issues,” she says. “A prison relationship is very hard to maintain.” Avery is currently serving life in prison without the possibility of parole.

Greenman says the two were engaged for a time, but ultimately she called it off. “We were going to be married in prison and I put a stop to it,” she says, declining to elaborate why.

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She adds: “It’s up in the air right now. It’s not where it was before – there’s just been too much strain.”

Still, they remain friends, and Greenman talks to him twice a week. She hopes that if he ever gets out of prison, they can have a real relationship.

“I can’t see him as a guilty person,” she says.

Last week, the White House responded to an online petition seeking a presidential pardon for Avery. However, because Avery was convicted of state offenses, the president cannot pardon him.

Wisconsin Governor Scott Walker, who actually does have the power to pardon Avery, has already said he will not do so.

Fortunately, Avery has secured a new lawyer, Kathleen Zellner, who announced Friday that her firm would assume Avery’s representation, along with Tricia Bushnell, the legal director of the Midwest Innocence Project.

“I’ve been working on her for four years to take the case,” says Greenman. “I’m hoping she can uncover new evidence.”