Glad you posted the above with more info. I went down a bit of a red herring wondering if there was any connection with Claudia Easom. I doubt it -most people in Oxford have bikes and a lot of people in Oxford are slightly older artistic ladies.
However, what worries me is what route this lady took with her bike. You can get onto the river and cycle into town or up to Donnington Bridge near her location. It is not unknown for a cyclist to get blown into the river. (My mother says this happened to her teacher when she was at boarding school in Oxford.) It also happened to a friend of mine's child when our kids were young -thankfully, another friend rescued them. They are looking for a bike. I want to know where the Eastern man who she may have been visiting to mend the flute lived as this might give a clue as to whether this lady took the river route towards town or Donnington Bridge. Hoping against hope this is not what happened. I see they think she came home again, but any trip anywhere on a bike might also involve the river if you live in that area. You get down to the river by the Four Pillars and it is a nicer trip to town than on the road. (Or up towards Donnington or Iffley or even beyond that.)