The fact that she asked if you could repair it means she trusts your skill and is comfortable with you. That's a great compliment! Every contact that you have with a current customer is a selling opportunity. You might tell her you'll take a look at the broken piece and, if it's within your skill set, repair it or refer her to someone who can. Give her an estimate up front for the repair costs (including materials) and make sure there's agreement on the work and any guarantees. Generally, repair work is an excellent way to maintain and even strengthen relationships with your clients.