What is this show about girls that use "spirits" to fight? Genre: Probably Shoujo/Fantasy or magic

Type of media: TV show/OVA?

Characters: Mostly girls with one main heroine and a male protagonist living in modern times (school attendance was probably involved)

Plot: The story revolves around girls with "spirits" they use to fight. The main heroine was using a "fire spirit" but only after she accepted it in one of the episodes. There also was a smaller girl, which was firstly her rival but they became friends after some time. The little girl was using a huge sword and in one scene in park lot she cut a car in half. Apart from the girls there is also a love story involved with the main heroine and a boy. In the end they have to fight some evil villain.

Time range: I watched it around year 2006?

I know this is as vague as it can get, but if someone could recognize it - it would be much appreciated!
Actually, the first title that appeared in my mind when reading your description were these three animes called....

Magic Knight Rayeart (MAL Page)
But then it only fits "The main heroine was using a "fire spirit" but only after she accepted it in one of the episodes ...The little girl was using a huge sword... In the end they have to fight some evil villain." and it won't fit "living in modern times"

But then, when I tried googling, I also found....  

Shakugan no Shana (MAL Page)
It fits "The main heroine was using a "fire spirit"..., ...firstly her rival but they became friends after some time. The little girl was using a huge sword too. Apart from the girls there is also a love story involved with the main heroine and a boy. In the end they have to fight some evil villain." and are "living in modern times".

But after searching more thoroughly, I found....

Mai-HiMe (MAL Page) Wikipedia Page
It seems to fit most of your description.

Sorry for this kind of random guess, but well even if none of them is the answer, at least it makes the possibility getting narrower...