Can i put a baby guinea pig in with an adult?

i had two guinea pigs. both females about 2 years old. yesterday Daphne died. Now Rosie(the other guinea) is alone. i am trying to take her out more often, but i still dont want her to be lonley in her big cage. do you think i could adopt a baby guinea and put her in with Rosie? or would they fight? what about an older guinea closer to her age? THANKYOU!