I read the other two responses and they are good but I want to make it more clear to you how the two phrases can mean very different things.
If someone says "She has played piano since 2005" that can only mean that she started taking lessons and has played regularly since then.
If someone says "She has been playing piano since 2005" because of the context you know that it means the same thing as the above sentence, BUT it could also mean that she has been playing piano continuously since 2005.
This sets up a good English joke actually... If someone were to say "I have been playing piano since 2005" you could say "Wow, your hands must be tired!"
Maybe nobody will laugh but at least you showed how well you understand English.