@raynbow- If you and your sister follow her doctor's instructions closely, she should be fine. Most patients simply want to rest after having surgery, so excessive tiredness or sleepiness are not concerns. Swelling and bruising around the surgical site will also occur. Feeling some pain or nausea are also to be expected.
However, if your sister develops a fever, severe vomiting, extreme bleeding from the surgical site, or severe pain, there could be a problem. Call her doctor immediately if you are in doubt at any point. Most physicians provide an emergency line for post-op patients to call at any time during the healing process.