Advice needed for sister (38f) and mom (65f) who excluded me (39f) from trip

I need advice on how to handle a situation: I had recently told my mom and dad( 67m) and sis of a trip I was taking in spring and also invited all of them which I realized later I did it out of habit and just wanting to include them so they didn't feel bad. They blew off the invite so I didn't think I had to worry and I just continued planning for just myself.

On a different time visiting with them my mom randomly said that they were taking another trip during the same time my trip was. They did not invite me and I said that was a bummer because I would have liked to have gone. But the timing wasn't right so NBD. My mom then asked if I would be available to watch their dog and I said I couldn't because I would be on my trip. So I figured they really didn't care about coming on my trip because they had even forgotten when I told them I would be gone.

Later I find out that their trip dates have changed and now my sis is asking when my trip is again so she can go on mine. None of them have invited me on their trip nor did they apologize for leaving me out. Even after I expressed interest in going none of them have said anything about including me. Basically, I need advice for how to word it to my sister that I'm hurt I wasn't invited on her trip and don't want to include her on mine because it feels like she's just using me to go on another trip. What is a good way of approaching this situation without burning bridges?