I watched the full video, and 6ix9ine never said he slept with Ayesha Curry. He didn't even mention who he slept with in the first place and was clearly reluctant to answer.

If you roughly summarize the conversation: Q: Who's the most famous woman you've slept with? A: If a famous chick in my dreams would give me head, blah blah blah~ Q: No, no, who is the famous woman in reality, I'm asking. A: Changing the subject blah blah blah~ Q: Stop changing the subject, yadda yadda yadda~ Q2: (Looking at the stream chat) Do you know Aisa? Who is Aisa? Ayesha? A: Ayesha? Ayesha Curry. Q3: Mumbling some other crap~ As you can see, 6ix9ine never even said he slept with anyone, let alone Ayesha Curry.

Maybe because the rumor spread so widely, 6ix9ine even denied the rumor himself.