For antibiotics, generally takes about 10 days for them to build up in your body and work most effectively. Tell her to keep taking them until they run out, and rinse her mouth as often as possible with saline (warm water and salt)...after every meal, every morning and night.
Tell her to get a second opinion, it doesn't hurt to have a fresh pair of eyes look at something the regular may have missed. Mouth pain fuckin sucks I know, so just try to be compassionate but firm. Also try warm compresses on her face where the abcess is located... it may help draw the fluid out.
[19-07, 22:39] dinosaur i have felt up ri2 before