How to train my 9 months old to drink from a cup? Or is it too early to train ?

My girl drinks from straw cup at about 7 months. She doesn’t know how to drink at the first attempt. I have to guide her using the end of the straw and drip water into her mouth. She could drink after that but water still leaks from her mouth frequently. After a month or so, she can now drink very well from straw.