In what circumstances does or would your character drink alcohol? (e.g. "with a meal, for fun, when depressed, at any excuse, NEVER EVER") Honestly, at this point? It'd be pretty damn hard to get her to drink. She's been around Tamaki and people like him enough to be a little wary of the idea of drinking, and getting drunk here and ranting at everyone over the network (and the ensuing hangover, of course) kind of cemented that. You could maybe get her to drink a little socially if you're persuasive enough and she likes you, and I could maybe see her drinking again if she's miserable enough (but being way more careful this time.)
How much would they normally consume? Do they get drunk every once in a while, or live and breathe alcohol, or make sure to stay under the legal limit? Not a whole lot. She's probably had to drink wine at high class social functions now and then, but given her opinion of Britannian high society, I think she probably skipped out of those whenever possible anyway, to the point where her stepmother stopped even trying to bring her. And I think she probably had a beer now and then just to be rebellious, but between the thing about Tamaki and Kallen generally having better things to do than getting drunk, I don't think she ever even got drunk before Marina.
How much alcohol tolerance do they have? Does even a sniff of alcohol knock them over, or can they guzzle alcohol without feeling impaired? Pretty low. She could handle a beer or a glass of wine, maybe two, but anything stronger would get her drunk pretty fast. Her metabolism is high enough that she could probably have a higher tolerance...if she ever actually drank alcohol.
What kind of drunk is your character? How would they act if they were drunk? Largely depends on the circumstances, but...in general, pretty loud. If you actually got her to drink when she's in a pretty good mood, she'd laugh a lot. Loudly. Whether it was funny enough to warrant laughter or not. She'd also probably get kind of clingy. If she's not in a good mood, she'd get ranty and irritable. And she'd probably start a fight...even more easily than usual.
Who would they go drinking with if they had to choose drinking buddies? Um...Lelouch would be an option, but he's probably too dignified, so she wouldn't even ask. C.C. could possibly goad her into drinking, maybe, but Kallen wouldn't ask her to drink together. Suzaku probably wouldn't be an option since it would be too awkward, with her semi-buried resentment/jealousy...but Gino would be a possibility. Although I can see her trying to start a drinking contest with him, and that wouldn't end very well. x3
What's their alcohol preferences? Beer, wine, mixed drinks with fancy names? Eh. Wine's okay, beer's okay, but she's never really had anything she particularly liked. She probably wouldn't touch the harder stuff, voluntarily, unless she was actively trying to get drunk, in which case the taste doesn't matter much as long as it does its job.
Green alcohol y/n? No.
Your character is completely drunk. Who do they drunk-dial, and what do they say? L-lol, haven't we been through this before? If she was in a bad mood, she'd probably rant at/about Lelouch and/or Suzaku, depending on who she's more annoyed at at the moment. So basically a repeat of what happened before. x3 If she was in a good mood, she'd probably call up anyone she thinks cares and ramble about inconsequential things. And laugh way too much.
...except in both scenarios, nothing would be filtered, so it'd effectively be to everyone in the whole prison. x3