sister love!

Hi ladies! I could really use some advise...I have a 5yr old that is overly happy and excited about becoming a BIG SIS...she constantly wants to grab her baby sister...kiss her smother her it's really cute but I also FREAK OUT...I find myself constantly telling her to STOP leave her alone:( I feel like such a Bad MOM! How can I handle this situation w/out hurting my 5yr old she's such a loving lil girl but I want her to be careful and understand the baby is small we need to be careful w/her. Thanks ladies!