The second or third approach
She now knows you’re here, knows what you look and sound like, and has got a general vibe off you, but she’s not been hassled.
Even if she did get that ‘Oh shit’ feeling that women get when they think they’re about to be joined by a strange guy they won’t be able to shake off, you’ve gone away right away, so her fear was completely groundless.
You’ve just proved that you’re confident enough to start a conversation, but you’re not going to be a creep.
Half an hour or so later, find a way to bump into her again (without it looking obvious) and make some reference to whatever you talked about earlier. The content of what you say doesn’t really matter, it’s just small talk, but it’s a chance for you to chat some more.
Again don’t make it seem like you’re there to stay, and make sure you’re the first to politely duck out of the conversation. This time, though, as you leave you can let her know where you and your friends are if she and her friends get bored of their inferior view / want to see how dancing is really done / anything else a little cheeky. Then you leave.
She might come over, she might not, but it’s up to her, and you’ve lost nothing. If she does come over – congratulations! She’s chosen to be talking to you, and now you can get to know each other some more.