EMILY: Regardless the funeral’s on Thursday. I thought we’d all go together.
LORELAI: Ooh, whoa. Two problems. Impossible to get away from the inn Thursday.
We learned in the Pilot that Lorelai attends business class on Thursdays, so she can certainly get away from the inn on that day. Perhaps she means that because of her class, she has to remain at the inn at other hours to make up for it, and that would clash with the funeral. How she knows it would clash when Emily hasn’t told her the time yet is a mystery. Another mystery is why she doesn’t mention her business class as another reason she is booked up on Thursdays.