I sent a flirty message to my friend and she just replied. What should I say?

So I've known this one woman for like four years and we mostly just hangout at this bar that we both like. She's invited me to things outside of the bar like concerts and stuff too. I like her and she knows but I've never really flirted with her outside of some playful comments while we were drinking. I sent her a message saying "hey are you going out to the bar tonight?" And she basically replied saying "she had plans all this weekend."

I replied "Awww ok I guess you'll just have to miss me until next time lol" and she replied with "Okay and a heart emoji." What do you think this means? How should I reply?