I not just don't think Yulia is stupid, I think she's clever. I don't think that someone who doesn't know that English is the most widely understood language in Asia is stupid, just that they are ill-informed. I found the whole way Yulia was trying to be clever and being tripped up by her lack of knowledge rather cute.
I think
staringelf is right that they had a lot of it pre-prepared and most of the questions they were asked weren't particularly difficult. But they often (particularly Yulia) came out with witty rejoinders to things that were said.
Those surely weren't all pre-prepared. You have to be intelligent to be witty like that. And as
convol said, you have to be clever just to make such ambiguous statements. I think Yulia understood the humorous side of what they were doing better than Lena, who tried too hard to be convincing.
The Popworld interview still confuses me. I would think that Yulia is intelligent enough that she would have realised the implications of saying 'yes'. Maybe it was a momentary lapse in her thinking, maybe she just wanted to surprise the interviewers and have some fun. Yulia had looked bored all the way through the interview up to then and was clearly enormously enjoying herself afterwards. It was terribly suspicious, but I don't know whether it shows Yulia as not being so clever, or her as being too clever by half. That was the thing with the MTV Asia video - Yulia was trying to be too clever by half.