Gosh, the opposite to Jinley, who has put on 2kg since hers!
At her check up the other day the vet said that they need a third less food after spaying normally (although she is show not worker).
From memory, Jinley lost some weight following the spay, mainly because she didnt eat for 3 days due to the drugs spacing her out!
If she isnt hungry then leave her as she is and if she is active during the season, then keep her food intake up. It might be the close season that you will see the difference and have to make adjustments.
If she loses any more mention it to your vet when you next visit.