I'd suggest a wee chat when she's calm, maybe asking her why she does it, and telling her why it scares you. Then agree on a rule ( something like, " stay beside me when we're out, rather than," no running off" ), and a reward and loads of praise when she keeps to the rule. You might want to let her suggest the reward ( within reason!) and keep a star chart, where she gets a star for staying beside you, and a simple, " sorry, no star today, as you didn't stay beside me", and certainly never take stars away. You could also decide how many stars she needs to get to get the reward, maybe only setting it at 3 or 4 days, so she gets the idea.