Yes, this is the humor of the age. For some. She's getting lots of negative attention too. But the fact of the matter is that with the nose-picking and sneezing, these are health issues. While my son is almost four (and loves to talk about poop.... ugh.That's 'potty talk' and gets him 5 minutes in his room away from the table if it happens at a mealtime, but is otherwise ignored), I have nannied girls this age.
You might have a conversation about this with her when the acting-up isn't going on. Explain that when she is picking her nose and waving it around, it's disrespectful. That sneezing on others can make them sick. And that you need to see a 100% turnaround before she can go out with friends anymore, because you don't want her to be this way in front of her friend's parents, and since she's not making good choices about this at home, then social activities are suspended. No playdates, no sleepovers, nothing. If she can't be respectful in her own home with her own family, you will not allow her out to be disrespectful to other families.
Then, pick an amount of time for her to show that she is changing this habit with everyone in the house. A week? Two weeks? Might be a good place to start.
*IF* she's a social kid, this might change pretty quickly. (Oh, and this also means no friends over to your house, either.) I'm not hot for punishments, but I also feel that this is somewhat of a logical consequence for these actions. When she does these things and you send her to her room, how long is it for, because I don't think the "1 minute per year" ratio Time Out is really appropriate for this sort of thing. If it were me, I'd be sending her to her room for a half-hour at a time. If it happens (deliberately) at dinner, then she may be excused from the table, and can finish her cold dinner (don't reheat it-- you are teaching respect) after everyone else has finished eating and left the table.
There's always one other solution, and it came from the mother of a teen. She's a very even-tempered woman, but when she'd had enough, it was enough. Her teen daughter was being rude to her, and the mom finally told her "You are going to have to stay in your room for the rest of the evening." Her daughter asked "Even eat dinner in here?" The mother, without anger, just said "Yeah. I don't really want you at the table tonight, because you have been so disrespectful to me. We'll try it again tomorrow. Maybe it will be a better day-- it's up to you." All that to say, that when we adults are calm and reasoned (because your daughter is doing it to push your buttons), I think the kids are able to 'hear' us better.
And when she gets interested in boys-- she WILL grow out of it. (I hope!:))