Hi there! My name is XXXXX XXXXX I would be happy to help you with your question! I'm sorry to hear Pua is in pain!
It sounds like your girl may be having some back issues! Sometimes if there is an injury to the back, a muscle spasm, or even inter-vertebral disc disease, it can cause dogs to be unable to travel down the stairs or get up and down on furniture.
This is something that you would need to have evaluated by a vet. You can get her in to have x-rays and have a physical exam, so they can determine from where her pain is originating.
At this point, it is probably not a good idea to give her any aspirin, as one of the main treatments they use to help with back and disc issues are steroids, and aspirin can have bad drug interactions with certain steroids.
There are also better medications to help treat the pain, such as Rimadyl or Previcox that your vet can prescribe to help her feel more comfortable.
Since she is in pain, you will likely want to get her in sooner rather than later, and you can locate a 24-hour clinic in your area with this website here if you do not already know of one.
If you have any follow-up questions or concerns, please hit "reply", and I would be glad to address them for you. Otherwise, good luck with poor Pua, and I hope she gets to feeling better soon!