To be honest, I think every single person in here is either exaggerating, or missing the point.

You want to give her a compliment, and whatever she responds, you want to use the second sentence, and leave.

So if she says: "Oh, thank you, It's funny you mention that since someone else did say the same thing yesterday. Either way, I'm getting a break in 10 minutes, want to get some coffee?"

Then you tap her elbow and say: "Just thought you needed to know." And walk away without responding to the damn question.

Do you see? It's put way too much in scene to work effectively, you expect some shocked or blushing girl, or that she will give a reaction that would make the second sentence an somewhat appropriate response to eject.

What if she had a bad day and doesn't want to talk to you? What if she told you to fuck off. Could you still attempt to touch her elbow and tell her you wanted her to know?

And the second fault is that you're supposed to open her, no one gets permanently opened by just a compliment, then touch and run. You're supposed to follow up, actually talk to her, if you think you won't have the time, don't engage at all and say hi at most. That's what an opener is for. What you're doing could be put in the category of funny bar openers like that 'did you come from heaven' shit and all it's variants.

If you HAVE to open with a compliment, make it sincere and sincere, and make it something that could follow up.

You: "Hey (name), could you do something for me?"
Her: "Yeah, sure. What do you want"
You: "That's great, thanks. I just love the sound of your voice, you know? It's like (insert exaggeration here.)"

That's just from the top of my head, but I think it'll do, referring to angels and heaven is advised. If you look like you're complimenting, and not sucking up, and actually look confident, you should get a very positive reaction.

But don't try to stage this too much and keep it natural, only touch when it seems appropriate and not just because you can.

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