Lei e'=she is, una delle=one of the, tue=your, ragazze=girls.
"The" isn't translated literally, so you pretend it isn't there, and you get "She is one of your girls"
Ciao stavlee: It isn't. It is "your girls". See answer, above, top of page.
are you sure about that? cause even though "una" is feminine, it still means "a", right? not "one"?
It can mean one or a. Just change the ending for the gender. If you think about it a and one mean the same thing in English, we just choose to use one word over another depending on the situation, but the meaning is the same.