I think isla is happy for the little attention she gets these days and also she doesn’t get to finish her sentences on a regular basis Jace always cuts her off and then the attention shifts to him. If they were a good parent They would correct Jace by saying wait a minute for Isla to finish then you can say okay. I feel Isla tries to get it all in as quickly as possible for that reason.The way that Isla rushes what she is saying, takes really deep breaths when talking, fumbles over her words and looks away when speaking all point to anxiety ( not saying she has is I'm not an expert just my opinion ).
My ex's daughter was the very same but for one main reason he kept shouting at her to hurry up in what she was saying causing her to fumble her words and get anxious about being shouted at, she was also ignored a lot by him which made her act out and crave his attention on the short 5 hours he seen her each week.
The little spark that she once had is slowing fading and its so sad to watch.