Female betta fish dying?

[Xandra]

My betta fish was an all red betta and then just a few minutes ago I noticed that she wasn't as red as she was yesterday. Is she dying? Did I not feed her enough? What?

 

[Vulcan]

Impossible to answer until you add details.

What size tank?
Do you have a filter?
Do you have a heater?
Do you perform regular partial water changes?
Have you tested the water?
Diet?

Fading coloration is generally due to stress.

 

[Min]

There are too many variables to answer your question in detail, you need to provide more info on what type of tank/bowl etc she's in, filtration, heating, water conditions, how often you do water changes?

One of the biggest mistakes is NOT heating the water for a Beta, any change in fish colouration is usually due to stress

Provide more detail & you'll get a better answer.