[CAUTION: I am not a teacher:take the advice and or corrections offered in this post at your own risk.
If you doubt the information, please get a qualified opinion from one of the teachers on these forums.]
Context, context, you need context. On the surface, yes "you are beautiful seems to be the statement. But if you are asking a question about such a direct sentence, it is probably because you heard/read it in a context where it doesn't really make sense, right?
Write that context along with your question. Used sarcastically, "you are a beauty" could be like saying "gee, you really messed up" or "wow, you've really made a mess of yourself/things"
Consider this as you go back to wherever you saw/heard this sentence. "she/it is a real beauty" could be referring to an object (like a vehicle, or a device) that is of very high quality as well.
Hope that helps.
Student or Learner