Unfortunately you see this a lot, it's unbelievable how much valuable ingame items can show you about a persons character. You have people like your GM who will give into temptation and nab the opportunity selfishly... and you also see the opposite where there are people who would be willing to pass entirely, just to let their friends have it and brighten their day a little.

Sadly that bit of bad was probably always lurking in your FC leader and this incident brought it to the surface and highlighted it.

However, this also comes as a blessing. You know their character without a doubt now and this means you can move on from a toxic enviornment and go out and surround yourself with the nicer people instead. You can take what you've learned and apply it to future frienships. Devote your time and effort into helping people who also have your interests at heart. There's no reason you can't find a friendly FC and enjoy the game with them. Your leader will already take a big dose of karma in that someone who's helped them through a ton of trials and with various FC activity is gone and all they have in exchange is a hedgehog.

See it as a new opportunity and being set free from catering to your leader indefinitely.