I don't agree with the advice to awkward about saying I love you to your in-laws. My sister in-law always says love you when we talk or part. It is very uncomfortable for me! I think saying thank you would make it way more awkward. I have resorted to saying love you too because I just don't know what else to do but every time I feel weird and dwell on it for a long time. It's not that I don't appreciate our relationship. I just only say I love you to my immediate family. I think next time I'll try a quick "you too" and make a mad dash for the door.