I don't know that you need to build more attraction with this girl, but if your gut was telling you she wasn't really into it then she probably wasn't. She did eject quite quickly after you told her she looks good. On the other hand she may have been flustered by your comment.
Like you said, you'll be seeing her again so re-enage and see how things seem at that point.
In the mean time meet more women at other venues/places as well.
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I go direct by telling her whatever she's doing must be working b/c she looks good.
In general you can subcommunicate this through your tonality and flirtatious manner. When you do this, girls know what's up through their intuition.