I would say it isn't because the inability to fly during cold weather is definitely a cold-blooded trait.
To clarify: whatever the reason the bee left the hive, when it gets so cold that it falls out of the sky, it doesn't die. It can lay in the snow, for all intents and purposes frozen, but it's not dead because of the cold. You take the poor girl inside and warm her up and she will be just fine. In order to die, she has to starve to death.
Warm-blooded animals are not like that. If they stay out in a temperature low enough that it interferes with their ability to stay warm, they'll die.