
I have had bitches bleed to 30 days from start of season and go on to whelp normally if mated, and have no issues re infection when not.
Assuming your bitch was mated mid season then this could still be just the tail end of the season, and mating will often restart the bleeding.
Remember we are checking our mated bitches rears far more after mating probably than normally.
If she is well, the discharge is normal (neutral smelling ) and not excessive, then I'd not worry, just monitor.