thats a toughie.... i was in the same situation. my boy, Raisin was on his own and we became ever so close before he died. we used to snuggle pretty much every night and i was his "degu-buddy"
i took the opinion, that regardless of how happy he was with me as his friend, it would ultimitaly be best if he had other degus around to chat with. i was given three girl degus who had the cage next door (no mixing
not only did he not show the slightest bit of interest in the girls (even though they loved him and flirted lots), but he started weeing on me everytime he came out on my lap, and marking me as his territory! not the slightest bit interested. so i ended up with one very clingy male degu and three females!
basically, what i'm saying is that, it is fantastic that you have this bond with your degu! its a lovely feeling to know they love you so much and depend on you.
BUT if there is a possibility that she could have a degu friend (and as she is young, you may have a better chance), it would be in her best interests! whilst i'm sure youre going to be the best degu mum in the world for her, you'll still never be a degu and be able to groom her/talk to her in the way she needs!
However, there is no guarantee they'll get on and you could end up with two clingy degus!