Introducing my two female guinea pigs?

[Leanna]

Both are six months and both are females.
I got my first guinea pig around june of 2010 she lived with my oldest guinea pig untill she passed away around the first of december.
So I got another female guinea for a cage mate. When I first brought the new one home I let the two out (outside the olds ones cage) to play on the floor and introduce themselves but the new one started fighting, like teeth chattering full out fighting.
So I separated them , I tried again a few days later and same thing.

What I was thinking it could have been is that the new one wasent adjusted to her new home and was just scared and thats why shes fought, because before I brought her to my house she lived with her sister for her who life so I know shes use to living in the cage with another guinea.

Im not sure exactly what to do, any advice?