Sources claim Rachel Doran pocketed £11,000 that had been set aside for him and 30 pals to celebrate on a trip to Ibiza.
And the 29-year-old is accused of handing over bogus boarding cards to the group at Leeds airport before vanishing.
When Chris, 27, and his friends tried to check in with Jet 2 Airways they were turned away. One mate said: “Chris was really embarrassed at the airport and couldn’t stop apologising.
“He was in shock and still can’t believe what has gone on. It’s going to take him a while to get his head round all this.
“He thought Rachel was the love of his life.” And a relative added: “Chris is mortified.”
Chris, who was due to marry Rachel in December, took to Facebook today to tell of his heartache.
He wrote: “Words cannot describe the pain and feels (sic) that are playing with my head today.
“I totally want to apologise to all my fantastic mates that were gonna celebrate what was supposed to be my stag do. I can’t apologise enough, I’m sorry boys I really am.”
He was supported by Rachel’s brother Ryan, who last night said he and his family had disowned his sister.
He posted: “Too good of a lad for a scumbag like that pal, she will get what’s coming to her.
“She’s got no f****r now. How a person can do something like that is beyond me. Evil cow. No morals.”
When asked by the Mirror where Rachel, of Cleator Moor, Cumbria, is he replied: “We don’t know.”
Friends and family rallied round Chris, who works at nearby Sellafield nuclear power plant.
Paul Dunn posted: “We all know you’ve been hit hard with this, pal, and I don’t think anyone could blame you for what she’s done. But everyone’s here for ya. Chin up pal.”
Sian Price added: “Thoughts with you Chris, your mind must be tortured with it all. You will be feeling what she should be feeling.” Chris’s mum Diane Casson praised his friends.
She wrote: “It’s heartbreaking thank you for being there for my son.”
After allegedly being dumped, Chris – who started dating Rachel in 2015 – headed to a pub in Leeds to drown his sorrows.
But eight of his pals booked last-minute flights to Magaluf in Majorca in defiance.
A Jet2 spokeswoman said: “We can confirm no booking was made, so the group were unable to travel with us as the flight was full.”
There was still no sign of Rachel late last night. A friend said: “The rumour is she’s staying on a caravan park somewhere.”