New partner for bereaved gerbil

Hello,
   
My gerbil was taken ill and had to be put down last night leaving behind her sister. She is only two yrs old and they were very close. I really don't want to leave her alone and was hoping to introduce her to a new friend. I have heard opposing things about what sort of gerbil(s) she would get on with best. Obviously it is harder to find an older single lady to pair her with but I did read that perhaps two female pups would suit her better, however, I have also read the opposite. I also heard that males are often best but I don't want to risk her getting pregnant at her age. I would obviously be using the split-tank method in introducing them.
   
I would be extremely grateful for any advice you could offer.
   
Thanks,
   
Anna

Introducing an older pup is a good way to go. Around 10 weeks old the pup will be large enough to fend for itself if a fight would happen to occur yet young enough to be easily introduced.