Should I be offended?

Okay so my mom picked my older sister up from work and when they got home my mom asked her if she “still wanted to go” I obviously didn’t know what they were talking about so I asked. I guess my moms bf wanted to go out to eat with my mom and sister but didn’t invite me?? Idk I’m like low key offended. He’s also said before that she’s his favorite... which is kind of upsetting too because she’s always the favorite when my mom is dating a guy or basically in general even with family. Idk but it kind of hurts ig