After seeing Games Workshop's new female Stormcast models, I wanted to do something similar for 40k.
I liked how they managed to make the models recognisably female without going full-on boob armour, and that's what I've gone for here. I made the torso section a bit bigger and put a slight curve in the front, pulled in the waist and pulled the hips out a little. I then reduced the shoulder pads to 70% size which also helps with posing.
Yes, I've read the blogs about how a "real" female Astartes would have the same armour as a male one, but that doesn't make for an interesting model and 40k models are about putting coolness over practicality.
The body is based on the Blood Ravens veteran model seen here: https://www.deviantart.com/lezisell/art/Warhammer-40000-Blood-Ravens-XPS-ONLY-742197921
The head is off Jaina from Heroes of the Storm: https://www.deviantart.com/lezisell/art/Heroes-of-the-Storm-Jaina-Pack-2-2-0-XPS-ONLY-702289875
Base is Destroyed Alien Bunker by Brexit: https://www.thingiverse.com/thing:3005454
The "Heroic" STL is the one I printed and painted in the photos.
The "Photo" STL is an alternate pose.
Bolter is included as a separate STL.
The "Mini" STL is designed to be printed small and shouldn't have any voids or mesh issues at tabletop size. (Second Mini version added 30th Jan 2019)
The OBJ + MTL version is lower-poly but includes textures.
The ZIP file contains an exported XPS file and texture files, so you can import the model into Blender and pose it however you like. Let me know if this works as I haven't uploaded this format before.
Printed figure, gun and base separately then glued together after painting.
Painted with Citadel model paints.
I know some dudes get funny about the idea of a female space marine so I made her a Blood Raven because they're the least hated chapter.