"I would be absolutely devastated if I wasn't invited to the wedding – it would be the last straw," Sherry, 43, tells Inside Edition. "They should elope if they can't have the Johnstons and the Palins together. But don't leave us out of it. That would kill me."
Added Levi's sister, Mercede Johnston: "I would love to be invited."
But while the Johnstons and the Palins have had their differences – mother-in-law-to-be Sarah Pain even took a swipe at Levi while speaking to Oprah Winfrey, with the former Alaska governor saying she understood that he had changed his name to "Ricky Hollywood" – Mercede still hopes for the best.
"I would love things to be put in the past," says Mercede, "but in all honesty, I don't think they're going to invite us. Wouldn't even tell us the date. It broke my mom's heart … You would think that a normal family would call you and say, 'We're getting married.' We found out through the media, which is heartbreaking and rude."
In December 2008, Sherry Johnston was arrested on charges of selling the prescription opiate OxyContin, which, she told PEOPLE , had her hooked after a 2001 hysterectomy. She later pleaded guilty and negotiated a plea deal that called for her to be sentenced five years in prison, with two years suspended.