Hi. Your skirt is too tight there. Legs and skirts move differently, if they are too close to each other, there will clip.
See how much tighter your skirt ( orange outline) is compared to a maxis tight skirt?
You need to go in MD and adjust skirt patterns to be less tight. In the future, start modelling garments by
importing maxis ones in MD and modifying them. It is much faster this way and they will fit right. To make them fit even better, you can split them in more patterns akin to how real world garments are made.
Other issues:
- your garment has no details like folds or wrinkles, its topology does not need to be this dense;
- the reference you chose was very different from your dress. It is much longer and looser, so your dress does not behave as its shape intends.
The leg area is where things differs the most in terms of moving and morphing. When choosing a reference, you want to make sure it is as close as possible to yours in length and overall shape in the leg area, first and foremost. In terms of rigging, it does not matter what the upper body looks like, the differences there are very minor. However, what matters are sculpted details. See how torn uv_1 is in the torso area? This is because the reference had a cardigan, along which the mesh is split. Just because your garment has it does not mean the reference needs to, you can transfer all data from yfBody_DressShortBands or similar;
- see how there is a skin colored line along every border of every pattern? this is why you bake texture with big margins, at least 6;
- you do not need to assign textures in MD, uvs and textures have to be re-done anyway;
- your dress is of flat white color. When you are baking textures, your MD texture must not be plugged into the material;
- your shadow and specular maps look strange. If you want to see what the garment looks like without them, just remove them with Make blank button;
- since you're making a garment in MD, you can make a high poly version and bake a normal map from it to your garment instead to get a much better result.
Here's an example of how to do it, in our case the extrusion has to be much lower because the avatar is tiny
