Translation:She has four older sisters.
To add to joaquintoral's anwer, the character 个 (ge) is also known as a "measure word" or "classifier". Each noun has a measure word. "Ge" is the most common one. 条 (tiao) is used with nouns that refer to long, narrow things like towels, roads, snakes etc., 本 (ben) with things that are bound like books and magazines. It takes time to figure this all out.
Because 姐姐 means older sister and 妹妹 means younger. Since there's a hierarchy in families you have to say older or younger
So there's no easy way to say she has four (older and younger) sisters?
Because in Chinese you distinguish between older sister（姐姐), and younger sister (妹妹）
'He' translates to a different character (他) and has the same pronunciation as 'She' (她).
在中国传统中，人称代词 “他” 是男女不分的， 既可以表示男性， 也可以表示女性。人称代词 “她”作为女性的“他”的历史很短，不过是在近半个世纪吧。 于是乎， “她”只能指代女性， 而“他”可以指代 男性和女性。
Neil, it would be helpful if you provided an English translation when you're explaining something using Chinese characters. I know I would appreciate it.
GT: In Chinese tradition, the personal pronoun "he" is a man and a woman, both male and female. The history of the personal pronoun "she" as a female "he" is very short, but it is in nearly half a century. Ever since, "she" can only refer to women, and "he" can refer to men and women.
what if she were the middle sister? How would we say that she has 4 sisters ?
No way to do that. You must say she have 2 older sister and 2 younger sister. Some of another East Asian languages have distinguish between older/ younger sister/brother, even the uncle who older/younger than father have different name, grandmother, grandfather who is father/mother of father, mother has different name. You must understand that East Asian countries (China, Japan, Vietnam, Korea...) have a high hiercharchy distinguishly social structure and their language reflect that. Dont apply "english" thinking when learning Chinese and another East Asian languages.
This is a problem across Duolingo Chinese: The audio version of this exercise doesn't allow for 他 OR 她 as correct answers. When it's written, the answer is clearly 她, but when you're asked to write the setence only from hearing it....then Duolingo needs to accept either 她 or 他 since it could be either one.