じゃないじゃん from context she seems to be it's the time to support that girl?
and "I don't have more free time. Pull yourself together"
In an uncontracted polite form, it would be 応援している場合ではないではないですか and this is a double negative in the sense that it contains two negative words, but not the kind in which they cancel out each other. A literal English translation that retains the double negative structure would be something like:
Do you not think you should not be cheering for that girl?
But since じゃん comes at the end of a sentence, it should be easier to understand it if you simply saw it as something like "right?" or "don't you think?" that you put at the end of a sentence in English.