She literally did though, but not physical health.
Timestamped at 4:07
I've seen many people detail how she's talked about having very big social anxiety, to the point of just sitting down and eating with people leading to her making mistakes and dropping food. She's apparently also talked about the moment a short while after debuting, when she rocketed past absolutely everyone, even her senpais, and became the first to one million, that she felt physically ill at the thought and started vomiting.
It's very clear that Gura is not someone that thrives in the spotlight. Instead it's the complete opposite. She's basically a big ball of anxiety and imposter syndrome.
I've seen people speculate that her frequent breaks could have been attempts to thin out her fanbase, and make people leave for others that streamed more. But if that's the case, it has spectacularly failed, and instead caused a viscous cycle of coming back to stream, get massive amount of attention for being back, get anxiety, and back on break, rinse and repeat.
There can of course be other things also, but this feels like the primary cause of her leaving, and with a full graduation instead of as an affiliate. Staying as an affiliate would still mean pressure that she'd maybe appear at some point. For this reason I also think it's not likely that she'd be very active as an indie either, as it would basically trigger the same "Gura is back!" cycle.
I think it's very likely that, while maybe not immediately, this is where she puts the content creator hat on the shelf for good.