Your sister's retirement is an important moment in her life. The gift you choose should match her acceptance of her new status. If she's very happy about her retirement, you should give her a gift that matches her well-deserved retirement. However, if you know that she isn't happy that she has to stop going to her favourite job, you can come up with something creative. This gift should cheer her up and let her know that you understand her feelings. I think it would be enough to give her some kind of gin gift related to drinks. I've always thought of drinks as personal freedom from obligations. If your sister thinks she has nothing to do in retirement now, you can turn it into a joke and tell her that she can finally put her all into herself.