If it were you and me, instead of saying "we are friends" you should say "us are friends". This the usual test I use to choose between those two when speaking. I think the right way is "You and I are friends"... I always get mixed up with "between you and I" and "between you and me". Since we doesn´t work there (it's between us, not between we), I choose "between you and me". I use this thumbrule a lot... though I'm never too sure it works...
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