"My friend helps me."
Translation:ידידה שלי עוזרת לי.
@jimmy930731: No, any noun can have the definite article, the possessive, both or neither in Hebrew.
הלכתי לטיול עם הכלב שלי - I went walking with my dog - strongly implies that I have only one dog.
הלכתי לטיול עם כלב שלי - I went walking with my dog - does not imply that I have just one dog.
הלכתי לטיול עם חברה שלי - I went walking with a female friend of mine - may or may not be my girlfriend, although using the word instead of yedida implies it.
הלכתי לטיול עם החברה שלי - she's my girlfriend - no ambiguity about it.
English distinguishes between "MY friend helps me" in which case you are referring to one friend. It does not say anything one way or the other about whether you have other friends, because you are thinking of the one specific friend who is helping. If you have in mind that the person helping you is just one among a number of friends you have, you would say "ONE OF MY FRIENDS helps me". Therefore, I would think the Hebrew equivalent of "My friend ..." would be החבר שלי and that the equivalent of חבר שלי would be "One of my friends..." or "A friend of mine..."