Oh I am just so sorry for your loss. I know exactly what you and your little Chelsea are going through. I lost my Tigger at 13 years (long story). His surviving playmate, Spanky, who was my "Porky Yorky", always having had a great appetite, went into a total decline when Tigger died, showed little interest in eating. It's a really good thing that your Mom is home with Chelsea..... she needs lots of love right now. She is grieving for her friend, even though he was much older than her. If she is only a year old, this was the only companian she knew after leaving her Mama and litter-mates.
As for getting another baby, I say each to his own. Sometimes one needs time to grieve the passing of a beloved pet. Other times, people handle grief easier if they have a new baby to shower with love. You have to do what is right for you. Because Chelsea is so young, there is a great chance another pup will restore her good spirits. Does she have any "small-dog" playmates??? In my area we often have Yorkie meetups..... something like that could be therapeutic for all of you.
Big hugs to both of you,
Lauren