non-religious guest for yomtov

Question

My sister who is not religious (or at most she is minimally observant) will be joining us for sukkot in israel form the US. I figure she is supposed to be keeping 2 days of yomtov according to halacha. I am suspicious that she will not, as she will see us not keeping yomtov she will figure whyshould she bother.. My worry is that I will end up doing melachas for her, such as driving if she wants to join us on a trip or various melachas around the house. If she elects to not keep second day yomtov, is there any problem with that and do I have to behave differently because of it? NOTE: I am not asking a shayla for her whether she needs to keep 2 days or 1. I am assuming she will rpobably keep only 1 and am asking how I should act in reference to her on the second day. Thank you,