It's the first time I've known the victim to be a cyclist, but in London we've had this type of robbery of pedestrians for quite a while now, done from light motor cycles, mopeds and even bikes. This sort of robbery seemed to have been common some years ago in holiday destinations, Spain in particular, but somehow migrated here.
London is full of people, but something must have prompted their selection of her, and the message remains as always, don't carry visible valuables or wear obviously expensive designer gear, since they are often the trigger for an attack. We accept we have to lock our homes and bikes, so by the same token we should take sensible precautions to protect our persons.