Hello, my name isXXXXX and I have over 20 years of experience as a veterinarian.
I'm sorry to hear that Luca was treated once already for Lyme and so of course I understand that you are worried that she may be infected again.
Has she had ticks on her within the past year?
Is she on a flea and tick preventative now?
How is she other then her limp?
Is she running a fever (rectal temperature more then 103.5F)?
Is she eating and drinking normally?
Is she bright, alert and active?
Is there any particular joint that is swollen on the leg she is limping on?
If she seems normal other then her limp (no fever, bright and alert, eating and drinking normally with no obvious joint swelling) then I am much less concerned about her waiting to see her veterinarian until Monday. This may not be Lyme disease. It may be a pulled muscle, an anterior cruciate ligament strain or tear (very common) or another injury.
You do want to keep her very quiet, meaning no running, jumping, stairs and leash to go out to eliminate so she doesn't overdo outdoors either.
What pain medication are you giving her?
If it is a nonsteroidal anti-inflammatory (like Rimadyl, Metacam or Deramaxx) then do not give aspirin as aspirin is a nonsteroidal as well and using both at the same time can lead to kidney or liver damage or gastrointestinal ulceration or bleeding.
If the pain medication is Tramadol then aspirin can be given with that.
Aspirin does cause stomach and intestinal irritation and ulceration as well as clotting problems so should not be given for more than 2 to 3 days consecutively and should always be given with a meal. If you choose to use it watch for lack of appetite, vomiting, blood in the stools or dark tarry stools and stop immediately if you see those. Do not use aspirin if your dog has liver or kidney disease or a history of a sensitive stomach or clotting problems.
The dose for aspirin is 5mg per pound orally every 12 hours (about one half of a 325mg enteric coated aspirin for a 30 to 35 pound dog every 12 hours). Always
give with a meal. Do not use for more than 2 or 3 days.
Be aware if you choose to use aspirin and it doesn't help your veterinarian will be limited on what they can give as there must be a 5 to 7 day washout period between different nonsteroidals or nonsteroidals and steroids.
If you can find a particular painful area(s) you can try alternating warm and cold packs on her painful areas for 10 minutes at a time several times a day.
Best of luck with Luca, please let me know if you have any further questions.