The fact that people think this is an admirable trait makes me sad.
Liara risking her life to prevent the Shadowbroker from obtaining Shepard's corpse is an admirable trait. It is also one that was crucial to the story, as the Shadowbroker intended to turn said corpse over the Collectors. If we accept that the Reapers win without Shepard, then Liara and Miranda are the two most important squad mates in the entire series.
That being said, I don't think it would be fair to criticize Ashley for not seeking out Shepard's corpse. As active duty military she had other orders and does not have freedom of movement. She also didn't have access to the same intel that Cerberus provided to Liara.