It turned out it was an abscess, caused because a tooth broke earlier in the week. The tooth broke because it had needed a filling but she'd not had it filled, her last visit to the dentist's being in 1990... Anyway, she got some antibiotics to stop her from dying of blood poisoning, and will have her tooth fixed (and the other two in imminent danger of going bonkers) under sedation next week.
As you may have guessed, she's something of a dentophobe. Nevertheless, she found it quite amusing when she got her receipt for the antibiotics that were going to keep her alive for the next week:
It was one particular line that caught her eye:
Not really what you want to see on a receipt for a prescription.
Apparently, the till operator's name was Siobhan De'Ath.