Adapted from a recent online discussion.

Question: My stepsister and I get along great and have a lot of fun together - as long as our parents aren't around. When my mom and her dad are there, she is snarky, mean, easily offended, easily offensive, and it's awful.

We've been talking about planning a vacation for all of us with my young son to Disney World, and it has already gotten contentious. A very large part of me wants to suggest we break this up and go to Disney with just me, my sister, and my son. But if my parents go, they will pay, and I can't really afford to go on my own. My sister could definitely afford to pay for all of us, but I don't think I should ask for that.

Any advice? This is so obviously a bad idea, but I don't know how to pull this off without lots of hurt feelings. I guess I can just go with it and put up with the sniping and anger in exchange for a free trip to Disney. Ugh.

Answer: The most obvious option is to back out of the trip. Say you're not comfortable being paid for and would like to postpone until you can save up for it. Two missions accomplished: getting out of this trip, and uncoupling the train from your parents. Three missions, if you count the whole independence thing.

Option two is to be more straightforward with your sister: "I don't know if you've noticed the same thing, but we seem to get along better when the parents aren't around." Could be interesting - but you have to be careful not to lay the blame on her.

Option three is to go on the trip as planned, but with a different attitude toward your sister. Someone who acts the way you describe is obviously stressed. Can you think of why? Can you find empathy? Can you help? Or maybe you can get away when it gets bad?

Even if you go with option one or three, file away two for another time. The underlying tension, rift, competition between you that corrupts your time with your parents is begging to be addressed.

Chat with Carolyn Hax online at noon Fridays at www.washingtonpost.com.