Alexander - She agrees with him. People with A names are definitely awesome, no questions asked. She would know him since she tends to know anyone and everyone her father knows; not to mention, Death Eater. Connections. Arden is all in with the Horcrux plot too. She needs something to do, so why the bloody hell not?
Daphne - Yes! They were in the same year, so they would know each other. Arden isn't big on making a ton of friends, but I think she'd like the Greengrass well enough.
Ginny - She can hate on her as much as she wants because the feeling's probably mutual, given that they're on different sides. Not very interested in people outside of her group.
Fleur - She... has no opinions of Fleur right now. Doesn't like her given her familial connections and who her familial connections are connected to. But things happen.