This is the second part of a series focused on Katawa Shoujo that now will be called "Broken Themes". As said for the post with Emi, this will have spoiler as well, for Lilly's path this time.
More often than not, Lilly is know as extremely nice and the happiest of the five routes. I agree with Lilly's route being the happiest, and she is nice, but sometimes she tries be kind to many people and end up spread to thin, and get to the point of ignore peoples feelings.
In some cases, I would describe Lilly as inconsiderately considerate, she is so concerned for not hurting anyone that she ends up doing what she is trying to avoid. That focus on not hurting people could be seen as motherly, which is also what I tend to hear from people describing Lilly, however taken to an extreme can be more self-serving. The reason being, the feeling of hurting a person affects you personally, to the point of, focus in caring for the person is lost completely.
The reason Lilly seems to be so considerate that it can be deemed inconsiderate, coming from one scene when you are having coffee with Lilly and you finally pry the thing that has been borthering her. She tells you that she will be moving to Scotland, which is nearly weeks before her departure. This could hurt a lot since Hisao was pretty honest with her, if you actually chose that, from the start and Lilly was hiding something that important.
Lilly hasn't been with her parent much, so when she got the chance to live with them she initially took the offer without getting opinions from her friends, not even Hisao. For the most part it seemed like Lilly was tossing aside the people that are close to for her family, who were too busy to care for her and Lilly's older sister Akira. However, it can be a difficult decision to make either friend or family, but when your friend are more of a family then your actual parents, I wouldn't have to think too much of that.
So when it came to convincing Lilly to stay with Hisao, both Lilly and Hisao had to act selfish without that mask of acting like they were being considerate. Hisao had to chase after Lilly in the airport, nearly dieing because of his heart condition, to get her to reconsider her position on moving away from him. While Lilly had to make her mind up that losing Hisao was more of a priority than being with her parents.
With Lilly pushing herself past being worried about people being hurt, at least in the good ending, I would say that considerateness was the root of problems with Hisao and Lilly's relationship. Which is the reason I would regard it as the theme of Lilly's route, and the only solution is to cut back and take a piece of its counterpart.