Later on in the story once Gwen is fully with you and "maxed-out" persay, you'll occasionally receive texts from her that give off Yandere vibes, such as saying she'll always be with you and nobody will take that away. Also sometimes before you leave the Manor she'll come up to you, sniff you, and tell you to not get any perfume from the city skanks on you. It doesn't affect the story though, just adds a couple extra little interactions.