Nope. Nothing (apart from your username, which is public) is ever stored unencrypted anywhere. Even your own Peergos server can't see your friend list. It is decrypted by your client when you log in.

We don't currently allow third party apps in Peergos, and when we do they won't be able to access the social graph, nor will they be able to connect to the internet, nor anything else outside peergos. So that data can't be exfiltrated.