If the girl shows up on time to work, at times is there for 25 hours straight for a shoot, and is professional, then what does it matter that she maintains a bit of distance from others? Maybe she is not someone who needs to socialize with people all the time and prefers other solitary pursuits such as reading... She is evidently not picking fights with any of her co-stars, so what does it matter what she does with her free time.
It is really in poor taste for whoever this 'anonymous' co-actor was who indulged in such gossip.