(and no offense whatsoever) I would hate it if my fav loved/cared for someone for years and they died and he/she was just "Ok...what's next on the agenda".
To me Liz mourning the loss of Jason makes sense to me. Could it get tedious? Sure it could when that's all the character is about...but Liz talked about Jason to his BROTHER (and I use capitals to emphasize NOT to yell. )...someone who loved and cared for him too.
It makes Liz more real and (gasp) likeable to me that she didn't just forget Jason (who's been her friend for years and the father of one of her children) like she has supossedly forgotten: Lucky, Emily and Nik (whom she's been friends with for years and years) and like carly has totally replaced Jason with Todd (with no explanation of why or how she can do so).