"She does not know what she will do in a camp."
Translation:Вона не знає, що вона буде робити у таборі.
Usually, in such kind of sentences, it is NOT omitted. It is possible but sounds a bit unnatural.
If you try omitting the second вона, it will even sound unnatural in English. Try it- "She does not know what __ will do in a camp". You need a subject before any verb
Of course it sounds unnatural in English, but that's a different thing. We say lots of things in English that would be entirely redundant in Slavic languages. For example "I put my hands in my pockets" - in most Slavic languages would be "I put hands in pockets". Who else's hands would one normally put in who else's pockets?