9” silent runner wheel would be a good option until she’s in a bigger cage. But gets expensive having to buy a temporary wheel and then upgrade it. But upgrading her wheel now will improve her welfare enormously and she will really appreciate it. (Not the Sandy track version - bad for their feet). Wheels need to have a solid running track - no open rungs - the wire ones are really dangerous and can give them bumblefoot).
Silent Runner Wheel With Sandy Trimmer Track And Cage Attachment - Exotic Nutrition