Calling for a date

Hey, I've noticed that most girls I've been dating , would rather not to decide if she's available for a date, till the day of the date. (that's happends usually when we're dating less than a month..) In my opinion most of the times it's just a test to see how much we're needy for them.

I've a strong feeling I make the same mistakes and failing miserably.
I'll give you an example with this girl i'm currently seeing.

I called her up, we had a normal discussion, my friend was on the other line..I didn't answer.

ME: "Listen, there's an interesting place I wanna show you tomorrow. we can have dinner and than go to see that place"
HER: "I haven't decided whatever I'm gonna visit my parents this weekend, they live out of town.."
ME: "If I were you I'll book a date with me while I can.."

She giggled and than paused. I didn't want to come of as a player (she already implied once that sometimes I sound like one...) and said I was just kidding and we'll talk about this tomorrow cuz I have to call back my friend, I think I was doing wrong when I told her I was kidding and lowered my value.

I need an advice how to avoid this waiting game and let her decide whatever she wants to meet and to put me on hold.

How much time is too needy for me to wait for her to come back with an answer till I make alternative plans and tell her I'm not available for tomorrow cuz she came back with an answer too late..?