CALL HER.
I’ll even give you a script.
“Hi. Yeah, it’s me. What are you doing tonight? Okay, tomorrow? Want to have dinner? I know this nice place. I’ll email you the details. Seven o’clock? Great.”
See? Wasn’t that easy?
Of course, there’s a much longer conversation waiting in the wings. Here’s a possible script for that. Say, at the very dinner you invited her to above.
"I know you asked me out before, and I know I said no. So I guess you’re wondering about that. Because, see, here’s the thing. I’m kind of nervous about it. I really, really like you. I think you’re smart, and funny, and beautiful. I was flattered that you asked me out before. But I guess I was worried that, if we did start going out, there would be something about me you eventually decided you didn’t like, and it would be over – and that would hurt. A lot. So I decided not to risk it. That’s why I said no.
"But I think I’ve changed my mind. You’re just as funny and smart and wonderful as always, and unless I’m mistaken, you’re still interested. I hope you are, because otherwise I’m making a colossal ass out of myself. If I am, please be nice about it.
"But if I’m not wrong, I think I’d like to try this. The hell with the risk. You’re a wonderful person, and I enjoy myself greatly when I’m with you. I think I would have a lot of fun with you, and I hope you have fun with me.
"And, y’know, if a month or a year down the line, it isn’t working out, yeah, that would suck, but I hope we could have this type of conversation then, too, because what I’m really afraid of is losing your friendship. If we try going out, and it’s a disaster, I wouldn’t want us to stomp off in opposite directions. I’d rather we admit to each other it was a mistake, and maybe laugh a bit, and then go back to being friends.
“What do you think about that?”
Here’s a little secret from somebody eleven years older than you: Women love it when you’re up front about your emotions and insecurities (well, to a point). They love it even more when it’s the truth. 
If you can master your feelings, so you come across as both strong and in touch with your heart… well, if she has an ounce of sense, she’ll have to restrain herself from jumping your bones right there at the table.
Keep us posted.