Zoe Gregory, a British Playboy model, accused Rodriguez of texting her to set up a threesome with him and another of her female friends. Gregory also claims that he sent her sexually explicit photographs just weeks before his proposal to Lopez.
The Sun printed a number of WhatsApp messages from Gregory in which Rodriguez allegedly asked her for "naughty videos." He reportedly asked Gregory, "She hot? Fun? How many times have you been with her?" about another woman and a potential threesome.
Gregory also told The Sun that Rodriguez also asked for "dates you can fly out (maybe next week to SF)," accompanied by a selfie showing his penis and thigh.
Neither Rodriguez's name nor his phone number are included in the text message screenshots published by the British news outlet.
Gregory claims that the text message exchange began after Christmas, which he spent with Lopez and their blended family and stopped in late January.
"He was being like a dirty dog. He seemed like a needy, horny bloke," the model told The Sun. "If he is doing this right up until the point he is proposing to her, it is just not fair ... J.Lo needs to wake up. I feel bad for her, and I don't think it's right."
It's not the first time the former Yankees player has faced cheating allegations. Earlier this month, former MLB player Jose Canseco tweeted cheating rumors less than 48 hours after the proposal, although they were soon debunked by his Canseco's ex-wife, Jessica Canseco, with whom he alleged Rodriguez was cheating.
Lopez seemed unfazed by that rumor. "She's heard the cheating rumors in the past and has never let it bother her," a source told Us Weekly at the time. "She trusts him and his love. They are inseparable and together almost all of the time."
Lopez has yet to comment on either scandal.
Meanwhile, Rodriguez has been showing his fiancée some serious love on social media. Earlier this week, he posted a photo of himself wrapping his arms around her on a golf course, praising her hard work in the caption.
"This beautiful woman starts shooting her movie tomorrow, 'Hustlers.' I won't play spoiler, but I can't wait until you see how she transforms herself into a completely different character!! She's been working so hard lately. I'm glad we were able to enjoy a quick little break before she dives into this new project. Love you baby and continue to shine, fly high and inspire all of us," he wrote.