Tryla's death seems much more to be there in order for Ahsoka to prove her point to Lux about Death Watch being evil. If we are going to say that she changed after 'A Friend in Need,' I'm going to say it had more to do with what happened between her and Lux during that episode than Tryla's death. I mean, I think she hasn't really ever been in a situation that she could develop strong feelings for a guy before. When she is suddenly put there (and kissed for the first time perhaps?) only to have him leave her at the end - I think that probably plays with a 14 yr. old girl's mind...even if she is a jedi. EDIT: Plus, with the "death" of Obi-wan, she really is forced to mature in the Hardeen arc for Anakin's sake, if we're all assuming the whole "child with an addict parent" theory.