Hello, I'm Dr. Deb.
I recently came online and see that your question about Nevaeh hasn't been answered. I'm so sorry that you've had to wait for a response, but if you still need assistance, I'd like to help if I can.
I can understand your concern about her, under the circumstances.
There are a number of antibiotics which would be appropriate to use for this condition but I'm not entirely certain that Amoxicillin will be strong enough, unfortunately. This is primarily because there seems to be a great deal of resistance to it. However, having said that, if you're seeing improvement, then perhaps it's effective for her. While I typically recommend culturing the milk from the affected gland to select the appropriate one, I will often begin antibiotics without one.
Cephalexin or Clavamox are my drugs of choice and would be safe for nursing pups.
I do have a few additional suggestions for you which may be of help:
1. Believe it or not, a cabbage leaf compress can be quite useful for mastitis since they can decrease inflammation. Apply clean, uncooked leaves directly to the affected gland and secure it in place with whatever you have. Change the leaves daily or as needed. If/when pups need to nurse, remove the cabbage compress to allow nursing and interaction, then remove pups and re-apply new leaves.
2. If the glands are not very painful, massage may encourage blood flow and help break up congested tissue. Cold laser therapy can be used to reduce pain, inflammation, and swelling and increase healing time but obviously you'd have to have her seen by someone skilled in this procedure.
3. I understand your desire to provide pain relief for her but I'd be a little cautious about use of Aspirin since it might potentially affect the kidneys in growing puppies. There's not a lot of this drug present in her milk but I'd rather be safe than sorry.
I prefer Tramadol for these situations but this is a drug which you'd have to get from your vet.
4. I typically do recommend that pups nurse on the affected gland if mom will let them or you should try to express the gland on a regular basis...again, if she'll let you.
The prognosis for most cases of acute mastitis is good, with resolution of signs within 2-3 weeks if treatment is appropriate. However, if Nevaeh is becoming systemically ill, then she may need to be seen by your vet for more intensive therapy such as intravenous fluids.
Since she's only been on antibiotics for a few days, I'd monitor her for now, encourage her to eat and drink as much as possible and treat as suggested above.
I hope this helps although, again, my profuse apologies for the delayed reply. Deb