Looking to buy these Chanel ankle boots - please help!

I called my SA quickly today to see if she could get the booties; she had them on hold for me yesterday and was waiting for my call today. I've got my fingers crossed.
 
Oh. I'm dying - I may have to part with my booties. I just received them this morning and they are loose around the ankle (or my cankle as I call it). I'm not sure if I need a half size down. I'm not sure how snug they should be, but these are mesh and won't stretch, so I guess they should be a little loose. My photo editor software is having an epileptic fit right now, so I'll have to post pictures a little later.
 
Pics of booties:

Here are the pics of the booties - they gap at the back and feet slide a little down the front. What do you think, do I need to go down a half size (to 36 1/2)? Did these come in half sizes?
 

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