If you don't floss frequently enough it makes your gums inflamed and then they will bleed when you do, so that's good advice.
Antibiotics are not prescribed to prevent things because they're not good for you if prescribed routinely. They're used when an infection has been established - not when it's suspected. You don't mention pain at all, which I am surprised by if you think there's an abscess.
If you have pain, max out on ibuprofen (because it's anti-inflammatory) and keep going back every few days if there's no improvement. It may be that an infection is starting but the dentist cannot see symptoms she could link definitively with an abscess or infection *yet*. Perhaps she didn't give you a temporary filling because if there *is* an abscess it needs to drain somewhere? If she filled it, any infection would have nowhere to go but down into the root and root canal work can cost you a small fortune, not to mention being uncomfortable and tedious at best.
Of course, nobody here (so far) is an authority on dental problems and even if they were, they might be hesitant to offer advice without examining your mouth properly. As a bunch of untrained fellow patients, most of us have nothing of significance we can offer you but sympathy! (And you do have my sympathy, that's for sure.)
Why don't you give the surgery a ring and ask the receptionist if you can speak to the dentist? If the dentist can't speak to you about it because she's busy, then a Practice Manager or Dental Nurse/Receptionist might be equally well equipped to convey the information you're after back to you. Sometimes, the best treatment is to act conservatively and see what happens when the situation is inconclusive. Dive in too quickly with the wrong treatment and it may only make things worse. I wouldn't judge against your new dentist quite so soon.
(edited for kooky spelling)
