Carolyn Hax: Moving away from clingy stepsister may not suffice to get her unstuck

I’ve already told Jenna I’ll be busy with my new job and won’t have much time for her, but I’m sure she’ll be blowing up my phone wanting to meet up, wanting help with some issue, wanting wanting wanting. If I ignore her, she’ll whine to my mom, who will message me, point out that my stepdad paid her portion of my college tuition, and say I SHOULD BE NICE and help Jenna out. Is there any way out of this?