No child would like to repeat a year in school, unless it is for a very good reason. Very few schools would consider her specific age to be a cause for holding her back. The best person to consult in this matter is your daughter.
I feel fairly sure that she will work harder on her own, if the alternative is to stay in the same class when her friends go up. Talk to her and more importantly listen to her. She has to be treated as a person in her own right, with views and values.
Gradually let her take responsibility to do her homework, etc. When there is somebody to remind them, children take the easy way out and wait to be told. If you put a lot of pressure on her for good marks, she will begin to feel that her value to you is directly related to her school performance. Surely, you wouldn't want her to feel that. Handle the matter with affection and it will sort itself out.