I think it's a veiltail female, but I'm not 100% sure. I kinda want to put in other females with it, but I don't want to be wrong and get any fish hurt. I think it's around 16 weeks old (I stopped counting after 12, so maybe older).
I have a few VT females that have that PK looking anal fin. Most people want this in a VT since it helps connect the anal and caudal better, making them looking more flowy together. This doesn't mean its a PK by any means, though.
That looks like a girl from the body shape, but the pics aren't super clear. If you look under her belly, you should be able to see a white dot. That is an ovipositor. Females also typically cross their ventral fins, but I've seen a few of my males do this too. I also have a few males with ovipositors, haha. I also have a female with male finnage!!! Most females have thicker bodies than males. Sheesh sexing is hard. -.-
Like... white dot in just the color, or white dot sticking out? I think I found I white dot sticking out... It does also seem a little thicker than the male I had. Sorry I couldn't get pictures, I only have the camera on my phone and it doesn't stay still. Also, I'm just generally bad at taking pictures. :v
The ovipositor will be sticking out behind the ventrals. Sometimes its hard to see, but sometimes its obvious.
In the end, to make this easy, her ventrals are very thin. If they were thicker, I'd be second guessing myself. However, they're very thin. Also, she has the signature female body shape. So I'm pointing to her being a female. She looks really full, too. Was she around any males when you bought her, or did she just eat?
I don't see why not. Size has nothing to do with sororities. Its more whether or not she's been QTed long enough and her personality type. I always bag up all of my girls and then release the new girl first. Some don't, but I do it for precautionary measures. I've had issues with the one time I didn't.