The answer to the question is to not allow yourself to be put in that situation in the first place.
First of all, you face two problems:
1. If you do call on Tuesday will you look like you are easily told what to do.
2. If you don't call on Tuesday will she think your rude or blowing her off.
Here are some ways you may consider handling it. If she asks you to call her on a certain day, then say, "Well, I can't guarantee I will have time on that day. Maybe I can call later in the week", or... how about, "Look, I know how incredibly interesting I am (wink, wink) and how attracted you are to me. But I don't want to promise I will call when I may not be able to. I'll have to get ahold of you later so you can be entranced by the honor of speaking to me."