Hi, your yorkie is very cute, first of all.
However, she is really too old to be bred, as others have said. I retire my girls between 5 and 6 years of age, unless they have not been bred very often and then I MAY do a 6 year breeding and retire at the beginning of the 7th year.
By the time a yorkie reaches the age of 6 and she has not had pups by then, she is most likely not equipped or able to handle a breeding at that age. Whelping is scary enough as it is, trust me I have had some horrible ones. You would not want to breed a female that is reaching mid-age. You face the risk that she won't know how to be a mom, or many other health complications that could happen with a female already 6 years of age. You face so many risks. In my opinion I would say absolutely not. I don't know any show breeders, or any reputable breeders, that would say to breed a female at that age for the first time.
Also, you mentioned that her topline is off. A topline that is off is SOOO very hard to ever fix. It is one of the most difficult faults in a yorkie to improve. A slightly off bite can be worked with, legs a little short or long probably, earset or tailset very possibly can be improved, but a topline is much more complicated. Even if you breed a male with a perfect topline to a female with a roached back (or even a slight arch), you will probably never completely eliminate it...and even if you did it would take years of work. Possibly the show breeders can back me up on this as well...
Honestly I would not attempt it...would it be worth it to risk your females life? At this older age they are already facing the risk of other health problems, I just wouldn't chance adding another one just to have a litter of pups.
Please don't take any of this as rude or mean, I am just trying to give you advice about your beloved baby.
