
It is quite nprmal for a bitch to be a bit mopey and subdied a few weeks after a season. She will return to her normal self though should be a bit more mature. This maturity is what you would expect and is one reason why I would never spay a bitch before at least one season, as I don't want forever puppies, as I prefer mine as adults :D
You will be wishing she will calm donw in a few weeks I bet :D