[Omelette]

She did knowingly make the Illuminati sign, but that's it - she's not a part of the ruling elite, clearly.

She saw Pav's t-shirt (look at OP's picture) and it reminded her of the Illuminati (Pav's t-shirt isn't an Illuminati t-shirt, but you can see how it would make someone picture Illuminati imagery). Upon seeing his shirt she just thought about those who she looks up to (bigger stars, bigger artists) who make that sign, and so, summoning the power of the 'big stars', simply made that sign to make big herself and the performance/dance up.

EDIT: Also, in the picture you can see how the front 3 housemates are smiling, however Pav isn't just smiling, he is smirking somewhat as he realises that Zoe's choice of the triangle was influenced by the imagery on his t-shirt.