Etiquette: How long should I wait for an email?

Sometimes I go three days without checking my e-mail. Even then, unless it is urgent, I may not answer an e-mail for another day or so.

Yes, you are, as you say, a "worry freak". Please stop that because quite frankly, worrying changes absolutely nothing. I bet that 99.99% of the things you worry about never even come near to happening.

She will contact you at her convenience.

Calling what quits? Waiting? No wait for two weeks.

Check the spelling of the email address.

Leave it. She will emai back if/when she wants to.
If you see her again before she replies you could check her email address to make sure it was spelt correctly. But people have run into this "I need a reply now" - she may only check her emails every few days. If it's not important she might not reply straight away.
And what's to call quits over? This person you met once? If she wants to keep in touch she will do. If not, never mind.

You just have to wait, how can you give up on waiting? You don't have to sit at the computer staring at your inbox just get on with other tasks and occasionally check your email throughout the day. Not everyone responds to emails straight away but if you have both agreed to email each other I'm sure she won't take long to reply.

You should probably email her a few more times just to make sure she saw your email. Like maybe ten times. You don't want to wonder the rest of your life whether she simply missed your email because you only sent one.

Typically, I would suggest to wait 0-5days, because people may get busy and forgotten to look at the email inbox. If something's urgent, I would suggest you to drop them a call.

you should not send another email until you get one back, some people don't check their email daily. Though if they have a smart phone they should be able to every few hours