Luann and Tom D'Agostino Announce Divorce: 'RHONY' Cast & More Share Shock  — 'It's Heartbreaking'

"My heart goes out to Luann during this difficult time," Tinsley Mortimer told PEOPLE exclusively

Luann D’Agostino‘s Real Housewives of New York City castmates were in shock when she made the announcement that she is divorcing.

After just seven months of marriage, the former Countess took to her Twitter account on Thursday to share that she and her husband of seven months, Tom D’Agostino, are calling it quits. “It’s with great sadness that Tom & I agreed to divorce,” she wrote. “We care for each other very much, hope you respect our privacy during this sad time!”

Although her costars had voiced their doubts about the former couple’s relationship, they were stunned to learn about their decision to end their marriage after less than a year.

Patricia Dash/Revery Weddings

“My heart goes out to Luann during this difficult time,” Tinsley Mortimer said in a statement to PEOPLE. “In life, some people think that it’s holding on that makes one strong; however, sometimes it’s letting go.”

Dorinda Medley, who set up Luann and Tom — and was a bridesmaid in their New Year’s Eve wedding — admitted to feeling heartbroken about the breakup.

“I’m just very saddened, you know. It’s always sad to see a marriage break up and obviously so quickly. I wish them the best. I’m just very sad. It’s heartbreaking, really. It’s heartbreaking for Luann too, because I love her and I know how much she loves Tom,” said Medley.

Patricia Dash/Revery Weddings

“As I said on the show, I’ll be here whenever she needs me,” added Medley. “When it goes well, when it doesn’t go well, I’m here.”

Sonja Morgan also extended her unwavering support to Luann. “I told Luann I’m there for her whether this worked out or not and here I am. Men come and go, and at the end the day, we have our girlfriends, don’t we?” Morgan told E! News. “I wanted it to work out, but I want her to know I’m here for her.”

Like Medley, Ramona Singer, who recently finalized her divorce from ex-husband Mario, also expressed her sadness over the split. “My heart breaks for her. Luann went into this wanting to make it work,” she told E! news. “I’ve never seen her happier.”

While Andy Cohen didn’t personally comment about the divorce, he retweeted Luann’s original tweet, as well as Dale Earnhardt Jr.’s statement.

“I just broke the news to Amy that one of the @Bravotv housewives announced their divorce,” Earnhardt Jr. tweeted. “I need the NFL back in my life, and quickly.”

Real Housewives of New Jersey alum Dina Manzo also commented. “I’m so incredibly sorry,” she tweeted on Friday. “Stay strong.”

The couple wed on Dec. 31 in a lavish wedding in Palm Beach, Florida, attended by several friends of the bride from various Housewives franchises.

But in mid-July, the pair weathered divorce rumors, with a source telling PEOPLE the couple had hit a “major rough patch.”

WATCH: Luann D’Agostino Announces She’s Divorcing Husband Tom After 7 Months

One insider told PEOPLE in July that many of the couple’s issues stemmed from “trust issues” related to lifelong bachelor Tom’s previous infidelity and flirtatious personality that had been causing friction well before the wedding.

“There have been a lot of problems,” acknowledged the source. “She felt he was using her for her fame and he went from Ramona to Sonja to her. He’s a Housewife groupie.”

Luann herself told PEOPLE just days after word of newlywed troubles surfaced: “What couple doesn’t argue? Tom and I have a very passionate love affair going and that’s why we got married.”

The Real Housewives of New York City airs Wednesdays (9 p.m. ET) on Bravo.

—WITH AURELIE CORINTHIOS