Brachypelma Boehmei male or female??

Leg length and abdomen size are irrelevant prior to a male maturing. You're seeing that its legs are longer and abdomen is smaller because it grew in size. This will happen just about every molt, until the male matures and is unable to successfully molt again, or the female has reached her maximum size. Your T looks a long way off from being an adult.

As far as the sex goes, the image is a little too blurry on the important parts for me to feel comfortable giving a concrete answer. You want a clear photo of the epigastric furrow - the horizontal slit that runs between the top pair of booklungs.

@Arachnophoric thanks for the reply. I'm new to the hobby so I'm quite unclear on all this but I'll try and get a clearer picture. I find the exo terra plastic almost impossible to get a clear photo through.

@KdeBruyn Not a problem! Welcome to the hobby, you've come to a great forum to learn.

That's the pain that comes with plastic enclosures, it makes it very hard to get a good image. If I had to guess based on this picture alone, I'd lean towards female. Your sling is still small, but as it grows it should become more obvious, and you can verify the sex by examining the molt. Sexing smaller specimens (ventrally or by molt) is a bit harder than sexing juvies or adults. For myself, at least.

I have another picture I can show post molt but I don't know how to post a pic on these forums lol

@KdeBruyn You can go ahead and upload it the same way you did this one.