The "fill-in" is the relationship that an SP will have while she is working until she is out and ready to look for the "real-deal" relationship. You could have a fill-in for years. You can love each other, accept each other, share almost everything with each other, but there will always be a cap on it. It will never be to what she is fully capable of giving emotionally. She will have love for you but never allow herself to fall in love with you. She can probably be more honest with you than alot of other people in her life. That will make you feel good except, she won't include you in her personal life. You won't be over to x-mas dinner with the family. You will always be a client. Maybe a special client, but a client all the same.