@Warpal
Too many guys in this thread are concerned about what she thinks about you and how you might appear to her.
That's a completely useless exercise. So what if she thinks you're butthurt or neurotic? She may hate your guts because you wore a green sweater, we have absolutely no idea.
Remember guys, what a woman or anyone thinks about you is absolutely none of your business.
Speak your truth and own it. The more effortless you can make this for yourself the better. Imo it sounds like low interest. Personally I don't reschedule on the same day, it throws my schedule off and you're right, it shows disrespect.
If she reschedules for the same day I'd simply say 'No I'm busy then, but I might be free later in the week.' I would let her put the effort in of rescheduling since she's the one breaking the date.
Or I might tell her where I'll be and what I'll be doing at her proposed time, basically saying 'I'm not going out of my way for you at that time, but you are free to come seduce me.'
If she doesn't reschedule or tag along with whatever I'm doing at her rescheduled time then bullet dodged, precious time saved. This is my personal style. Some guys don't mind chasing and rescheduling a million times. I do.