Most likely. Not because she is looking pregnant but because they store sperm. Normaly a female has to spawn several times without the presence of a male to be "free" again.

I personally would just get floating plants or spawning mops in the main tank and let her give birth in there/pull the fry after. In my experience, the stress of being in the box (especially when they aren't about to give birth) can/will kill them. You'll know when the female is about to give birth when she starts taking on a boxy shape (it'll look like a double chin kinda except it's her chest), the dark spot will be very large, she'll be aggressive and hiding in one of the corners of the tank, and not responding to food. That's when you'd pull the female, if you urgently want fry.
That dark spot in the posterior of the lower abdomen usually means more fry on the way.
View attachment 1512898
You can see the same dark spot in the Xiphorus mayae female above.
The darker it gets, the closer to dropping fry she is.
Technially that spot just shows that the fish is sexually mature. It does not mean that the fish has to be pregnant. Though it is very likely when it was pregnant before. The spot can be darker or lighter in different individuals. Some have a very dark spot from the beginning on, others show a development from light to dark during the pregnancy. In some fish, often in lighter pigmented specimen, you can even see the fry through the skin.So mine is going to have some very soon then. Her spot is very dark