It's actually much harder to maintain a relationship in which you don't live together—you have to work harder to build trust, intimacy, communication, patience, time management, etc. That is not easy! On the plus side, you don't take each other for granted and focus on the things that bother you about your partner, which everyone does. There's less conflict.

Louise's house is not set up for a toddler nor does she want it to be, and thus she doesn't like his daughter over her house, breaking things and making a mess. It will be different when she gets older.