GOOD Morning America” co-anchor ROBIN ROBERTS is being urged to protect her $125 million fortune with an iron-clad prenup before marrying her longtime lesbian love!

The beloved cancer survivor, 53, kept her sexual preference secret for years but finally came out via a Facebook post on Dec. 29. Now, insiders say, she’s ready to wed her leggy blonde girlfriend, Amber Laign.

“Robin’s family and friends are overjoyed that she can now seek the life she wants with the woman she truly loves,” a source told The ENQUIRER.

“But at the same time, they’re concerned that if the two ever divorce, Robin could lose half the fortune she’s earned as one of morning TV’s highest paid personalities.”

ANOTHER SOURCE ADDED: “Legalizing her union with Amber will bring Robin incredible joy. But Robin has had previous relationships that ended in heartbreak, and those closest to her want her to deal with her upcoming marriage realistically.”

As The ENQUIRER reported in March 2013, Robin was heartbroken over a breakup with fashionista Storm

 Sahara. She’s also been linked to former Auburn University women’s basketball coach Nell Fortner. Robin ended speculation about her sexuality when she publicly thanked Amber, a licensed massage therapist originally from the San Francisco Bay Area, in her year-end Facebook post. The two met through mutual friends and Amber, 39, now works in New York City, specializing in patients recovering from serious injuries.

In the past few years, Robin has gone public with her health woes, including a battle with breast cancer in 2007 and a bone marrow transplant in 2012 to treat the rare blood disorder myelodysplastic syndrome.

During Robin’s latest or­deal, “GMA” regularly aired updates on her health, and she visited the set during her recovery. Viewership soared, and “GMA” toppled NBC rival “Today” from the top spot in the ratings.

Just 10 days before coming out on Facebook, Robin – who’s already worth $25 million – re­portedly signed a whopping $100 million five-year deal with ABC.

“If Robin and Amber live happily ever af­ter, they’ll be fine,” said the source. “But if they split, Robin should have a prenup that ensures she’ll keep all of her hard-earned fortune.”