The former All Saints star has been rocked by allegations the former Oasis singer has a seven-month-old daughter with journalist Liza Ghorbani, and has flown out to Orlando with her and Liam's 12-year-old son Gene to spend time with her sister Natalie and her family.
A source told the new UK issue of Grazia magazine: ''Nicole had to face reading about the allegations in the paper and hearing the speculation. They were in Ibiza together at the time.
''She was livid and confronted Liam but he assured her it was all lies and that the child wasn't his. She fled to be with her sister while she sorts her head out.''
Beady Eye frontman Liam is accused of fathering a child with Liza after embarking on an affair after the pair met when she interviewed him for the New York Times newspaper in 2010, and the journalist is now demanding £2 million child support from him for her daughter Gemma.
Although Nicole, 38, enjoyed a family day out at Walt Disney World, she was said to be looking strained at dinner back at her Orlando hotel
A source said: ''Nicole is putting on a brave face, but has moments where she slumps into the depths of despair. It is hard to accept it could be over just like that.''
Nicole and Liam, 40, have been in a relationship since 2000 and got married on Valentine's Day (February 14) in 2008.
Take a look back at October's inaugural event.
The film is expected to continue without Mendes' involvement.