Found a high-res ver. of their first magazine pic:
Interesting things to note:
How Mizuki refers to the others: "Erina-chan", "Riho-chan", "Kanon-chan"
What this says to me: She's being friendly with everyone.
How Erina refers to the others: "Mizuki", "Riho", "Kanon-chan"
What this says to me: She's closer to Kanon than the others.
How Riho refers to the others: "Fukumura-san", "Erina-chan", "Kanon-chan"
What this says to me: She sees Mizuki as more senior.
How Kanon refers to the others: "Fukumura-san", "Eri-chan", "Riho-chan"
What this says to me: She's closer to Erina than the others. Also interesting to note that she thinks Mizuki is "older-sister-like".
Might do some rough translation summary of some of their other comments later.