DEAN: Why don’t we just bring [Lorelai] something out?
RORY: No. She and Luke have been in this fight for too long, she’s gotta do this.
DEAN: You’re cruel.
RORY: Tough love, baby.
Tough love is the act of treating a person harshly or sternly with the intent to help them in the long run. It is thought that the phrase originated with the 1968 book Tough Love by Christian community activist Bill Milliken, who worked with at-risk youth to keep them engaged with the education system.
Dean describing Rory as “cruel” seems quite apt, considering the dishonest basis of their relationship at this point.