My cat was treated for 1 whole week - we used penicillin we had from my dog (made sure it wasn’t expired for full best effectiveness) dosed according to weight - and of course it was a cat not a rabbit - I’m assuming you are also dosing according to weight? (I’ve asked her for a dose chart by weight from her veterinarian and I’m going to get one from my personal one - I like to double check data - and I will post here hopefully tomorrow

)
my sister works as a vet assistant (she aids in surgeries and administering meds) she said sometimes may take longer depends on each animal - should be 100% gone by second week ! As long as you keep administering twice daily(morning/night)
she said if not seek medical attention as it may not be mastitis

I hope it is and she will recover perfectly fine!
keeping kits away will help dry up faster ^^ . But rabbits have very good hearing - and if you ever breast fed your own kids you may know - sometimes your boobs leak when their crying - natural body instincts - and the same will happen with any mama regardless of species (it’s not all the time or with everyone) so just try to make sure she can’t hear them - just in case - as it will prolong the milk production