hey OP what crowd of chicks are you dealing with? No offense but assuming since you said you smoke weed, do the chicks your going after do drugs and shit as well? These girls always seem to be more difficult then regular party bitches. For some reason(as ive seen with friends trying with these girls) they have soo many issues that they get caught up in and because of that they may be to busy to do anything real with their life. Such as if they chick is a pot head, shes probably looking to smoke out or score weed from with whoever and from whoever...main goal other scenarios coming second.
Or it sounds like shes trecking to see if you'll chase her....most classic test in the book...bitch tells some dude she wants to get together/or shes very forward with him just to see how he'll act. Depending on how one handles from that point on could decide the fate of yes or no.
Ive seen a couple girls run on this guy with similar shit, we started talking about doing something later in the night..dude suggested about going for a ride on a buddies vessel in the river. This chick gets instantly excited saying oh yea ill show up for that, can i bring friends, starts naming off people, sounding anxious etc etc. SOUNDED INTERESTED AS FUCK...had me fooled even(except i would've handled differently see my personal experience later)..what does this dude do, flips out within seconds starts trying to make plans right away. Right then and there calls his friend asking about if he can make it happen. Then I noticied seconds later the chick was quiet and was seemingly more quiet, not asking any more questions or anything about the ride.
PAUSE
What just happened right there? This clever bitch set this dude up to see how "far" he would go out on a limb to try to sway her and go out of his way to set things up. You can all guess what happened...I called later(6pm evening) asked if it was setup, OH YEA BRO THE GIRLS AREN'T COMING but we are still going. Go figure right, chick tells the dude the day after she had a serious hangover....at 6pm? HAHAH keep in mind this whole ordeal went down in the afternoon with plans to go later in that night. Doesn't make sense how you can obtain a hangover with in a few hours without drinking
NOW having it happen to me with a bit of

better handling. I cant remember all the exact context but it was very similar to above but with a very similar flirty chick.She told me she was free saturday night, so I ask whats to do? She said she didn't care im not picky. The breeze of how she said that bothered me, idk why but it did.I Decided on a movie and a general time to go that weekend. So basically i ended a conversation with the "possibilty" of going that night, it was not in stone really, sort of knew from the way she was talking not to push anything. Called that day, 30minutes to get ready and go pick her up. Simple.
A flake is a flake, but sometimes depending on if you can handle and your attitude towards things may have a HUGE role in your fate.