After I checked raw version, both interpretations are actually right. But when you looked into contexts, it's kinda lean toward "Getting a Cosplayer GF". I think some are seeing it as "I can become [noun], [noun], [noun]".
Knowing Bocchi, I highly doubt she want to be a cosplayer herself, eventhough the idea is that "she can be [anything]" but I don't see why getting good at game is crucial to "be Cosplayer GF". And why specifically "Cosplayer GF" and not just "cosplayer" then?
As someone mentioned it already. This way, it'll line-up with Japanese audience's comments.