There were all sorts of rules about knights not running away. Robena was of the opinion that they applied mostly in military contexts and that applying them to supernatural issues was why manticore lairs tended to be surrounded by skeletons in full plate. Nevertheless it is still deeply, deeply difficult to bring yourself to withdraw when your trained reaction to danger is to set your feet and raise your shield. It's pointless, she [i]knows[/i] it's pointless, but she is far too scared to do anything as brave or complicated as running away.

"Constance? Constance!?" she calls, trying to back up so she's got a wall behind her. "Help! Please!" 

She's honestly too scared to really take the accusations to heart right now. She will likely brood over them later, but the frightening thing here is being approached by a group of ghosts and not having to litigate the honour or lack thereof of following her sworn liege on pilgrimage.