Relax, if she's approaching you while you're working, she hardly dislikes you. Just try to calm down and be yourself, you already said you were talking to her, so you can talk to girls. You just need to try to get more confident in yourself, and then it'll be easier. Maybe next time, if you don't think you're good at talking, you could just ask questions (not a lot, don't interrogate her), and just listen to what she has to say. And that might give you some time to breathe and think, and then words might come easier for you.

It's definitely a good thing though, if she's starting conversations Good luck!

Don't be so hard on yourself. I think you feel this is a bigger deal than it really is. Don't count yourself out before you even try. Maybe you're reading too much into it and she wasn't really sarcastic with her reply. Just relax and be yourself. Anyone that wants to change you, or doesn't like you for you, isn't worth your time. You're forgetting that she was the first to approach you, so that's a positive sign. If anything, it shows that she was at least willing to strike up a conversation with you. Don't worry so much about what you're going to say. Just talk to her like you would to anyone else. Be confident in yourself and smile and be friendly. The more you think about everything negative about yourself, the less confident you'll be. Start looking at your positive traits and don't bring yourself down. I suggest you try talking to her when you see her again, and see how that goes. I also suggest you get talking to other people, too. It's easier to talk to people you aren't attracted to, less pressure and whatnot. You may even make some friends and it will help build your social skills and confidence.

Just be yourself, if your not a funny guy dont try and be, and if you are, dont get too ambitious unless youve got the confidence to pull yourself out of a mess, if something backfires on you, take the piss out of yourself, that is guaranteed to get a laugh