That's horsecaca dude. I don't know what type of chicks you go out with, but I like ones that actually have a life that is interesting and fun, much like mine so that we can get together and do fun sh1t when we're together. If she tells me once she can't do something, I don't read too much into it.
You don't kick a chick to the curb because she has something else going on. Now, granted I can't tell much from his description. It really depends on tonality and such. Something that I can't really put in a post. I would call her, just bust on her, have fun, kid around, get her emotional and such. And then invite her to coffee, or a walk by the lake etc. If she said something like "<sigh> I have to bikini wax my grandmother, no thanks.", that's one thing. If she however says, "When?? Oh drat, I can't make it then, I'm getting my implants reinflated. Can we do something later instead?" That's different. So much is in the tonality in the voice. However, you have to build up those emotions, again.
If you call, talk about silly bullsh1t for a few minutes, then ask her out. You'll get flamed. However, if you call, bust on her, get her laughing, tease her, etc. And then come out with "I know we'll probably fight like cats and dogs, but why don't we get some coffee on Sat morning, what time is good for you." That's an easier sell.
Just my opinion.
M