I must have read these books aged around 11 -13, so late eighties, and I would love to find them again. They were about a girl called Rose who time travelled on a magic horse, she went back in time and had to help people sort out some sort of problem in the past (very Quantum Leap)! There was also a mysterious man in it (friendly), can't remember his role exactly. It sounds crap but they were based in a city and the magic horse etc was in contrast to the quite deprived area it was based in or at least that she time travelled to.
Does this ring any bells? I remember 2 books but might have been a longer series. I was obsessed with them at the time.