It is uncommon for luxating patellas to affect small breed dogs that much. Often, if they are not wanting to walk around then there is also cruciate ligament involvement. There is a slight chance it could just be really bad patellas, but if she were my dog I would want an opinion from a board certified surgeon prior to going forward with surgery. I recommend the LVVSC surgical department if you have not already consulted with them,. They are not the cheapest for surgery, but they are experts and you know that they will be doing the procedure that best for your dog. This is a situation where it may be better to postpone while saving money, instead of risk a poorly done surgery (of course I would consult with the surgeon prior to making that decision).