Ok, for the last few Tia, Luna and Twi pics. It seems like Luna was being dragged along as a third wheel.
Now we see that Tia got Luna a... *ahem* ... date. Thanks to Ask Princess Molestia. I have grown comfortable with the DerpyLuna shipping. So thats what I think when I see this picture. It may be the lighting you used for the picture but Luna even looks like she is blushing.
Tia's plans are working though. Drunk Twi is much more fun... for later.