Agree. I don't think orbiting in the circuit is a safe option. Better to extend or climb into the overhead and start again if slowing down isn't an option.
This is the right answer.
Only ever orbit at controlled fields with ATC instructions and ultimately they're keeping an eye on the spacing.
At an uncontrolled field, you have no idea what's behind you, and they may not even have a radio, so orbiting is quite unpredictable and could lead to lots of confusion, as well as the solo student controll issues you have raised.
Extending downwind also has the problem of making the circuit longer and longer for everyone behind.
As above, the only real options are to slow down, or if spacing is too tight, go around and fly another circuit.
I don't really see extending upwind as a solution, as you would have to realise the spacing will be tight so early on, I wouldn't expect that level of situational awareness from a freshly minted PPL, let alone a solo student.