Can female Rosy Barbs become male??

Hello!
(its been ages since i was last active)

I've come here to ask a question because I have observed that over the past few months, my female rosy barb has developed the colouring just like my male one. She is much more bright and vivid, her fins are partially black but also chases around the male now which previously, it was the other way around.
I know that some animals can change sex but isn't that species specific. Is my female rosy barb just really healthy or has actually become male?
I'm confused myself.
Before:



Now:




As you can see, there is a great difference between the pictures. Is it possible for rosy barbs to change sex or has someone just swapped my fish?

They don't change sex. You probably had a young male (they have the same colouration as a female) and has now shown its mature male colouration.