
I assume as you refer to bleeding rather than discharge, you mean obviously red blood? If you're talking about a murky and/or smelly discharge, with those timescales I would be concerned about the possibility of pyometra, which is uncommon following a first season but definitely not unheard of.
As another poster said, your other bitch being in season could have brought her back in, but if you have any suspicions that she's under the weather or if you see her drinking excessively, it may be worth checking her temperature or getting your vet to check her over.
Marina