Melania Geymonat says the men made sexual gestures and demanded that the two women kiss before they attacked.
Five people have now have been arrested over the violent attack on a gay couple on a bus in London.
Melania Geymonat, 28, from Uruguay, and her American girlfriend Chris were on a night bus heading home to Camden, north London, on 30 May when a group men started to make lewd comments and asked them to kiss.
The women were then attacked and punched several times before the assailants ran off the bus.
Melania Geymonat had a swollen black eye several days after the attack
Melania Geymonat and her girlfriend Chris were punched several times
The Metropolitan Police previously said four males, aged 15 to 18, had been arrested on suspicion of robbery and aggravated grievous bodily harm.
Investigators have now said a fifth suspect has been detained.
In a Facebook post, Ms Geymonat, who lives in Bishop's Stortford in Essex, said the pair had been sitting on the top deck of a double-decker bus and there appeared to be no one else around when the incident happened.
"We must have kissed or something because these guys came after us," she said.
"They started behaving like hooligans, demanding that we kissed so they could enjoy watching, calling us 'lesbians' and describing sexual positions.
"In an attempt to calm things down, I started making jokes. I thought this might make them go away.
"Chris even pretended she was sick, but they kept on harassing us, throwing us coins and becoming more enthusiastic about it."
Ms Geymonat said her girlfriend confronted the men and three of them began "beating her up".
After trying to intervene, Ms Geymonat said she was also punched.
She said: "I got dizzy at the sight of my blood and fell back. I don't remember whether or not I lost consciousness.
"Suddenly the bus had stopped, the police were there and I was bleeding all over."
Both women suffered facial injuries and were taken to hospital, while Ms Geymonat added she may have broken her nose during the ordeal.
The attackers also stole a phone and bag from the women.
Ms Geymonat said one of the men spoke Spanish and the others had British accents.
Prime Minister Theresa May called the incident a "sickening attack" and said her thoughts were with the couple.
She added: "Nobody should ever have to hide who they are or who they love and we must work together to eradicate unacceptable violence towards the LGBT community."
London Mayor Sadiq Khan described the incident as a "disgusting, misogynistic attack" and said hate crimes against the LGBT+ community "will not be tolerated in London".
In her social media post, Ms Geymonat said she was tired of hearing about gay friends being beaten up "just because".
"We have to endure verbal harassment and chauvinist, misogynistic and homophobic violence," she said.
Detective Superintendent Andy Cox said detectives were currently reviewing CCTV footage of the attack, and urged any further witnesses to come forward.
He said: "This was a disgusting attack on two women who appear to have been picked out and targeted by a group of youths.
"A number of active enquiries are in hand to trace other individuals suspected to have been involved in the incident. Lots of people will understandably be outraged by this attack.
"Our efforts to trace all the suspects involved and bring them in for questioning will be relentless."
Stressing that such attacks on London buses were "rare", he added: "I would like to reassure those heading out over the weekend that extra uniformed and plain clothes Safer Transport officers will be out on patrol working to keep them safe and prevent crime."
:: Anyone who witnessed the incident or who has information that could assist the investigation is asked to contact police on 101 or tweet @MetCC and quote CAD737/30May. Alternatively, call Crimestoppers anonymously on 0800 555 111.
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