Help! I'm afraid to ride my horse after an extended layoff.?

A little background info. My 12 y/o TB mare fractured her coffin bone 4 months ago and has been on stall rest with limited turnout. The vet has given me the ok to start riding her again for about 10 mins per day, walking only. She's very sweet, but I am still nervous to get on her after such a long vacation. Does anyone have any suggestions to make these first few rides "uneventful"? I would normally lunge her if she was being fiesty, but I am not able to do that due to her recovery. (Trotting on a small circle would put too much stress on the injury) Thank you soo much for any advice.