You have full permissions for Rin here. She has no canon strong psychic resistance, but magi in her canon naturally do. It's kind of a grey area when it comes to Fate/Extra canon because they're descendants, but they skimp on a lot of the world building inside the actual game. Since Leia is specifically trained though, I'm willing to say she probably can break through most of Rin's stuff.

Rin's a temperamental girl who is quick to act differently than how she feels AKA typical overblown tsundere. I'll try to keep that in mind for our threads, so feel free to read anything in bracket text.