She will turn pale and show horizontal stripes along her body, and try to hide.
Your betta fish is a female if she has smaller fins than an average male.
If you would like to know what gender your betta is, look for the egg spot. (for females) It should be a small white cloud between the head and body. If your betta has one, it's a female. If your betta doesn't have one, it's a male.
Female bettas are usually less colorful and have short fins.
Maybe your female betta is a lesbian lol
Female beta is a murderer.
A female Betta in breeding condition will look plump and have a rounded tummy area.
Male betta's are more colorful then female's
When a female beta is ready to breed she develops a horizontal line the length of her body.
From a female Betta. Then the male Betta fertilizes them when they breed together.
If the eggs in a female Betta are not laid, they can become reabsorbed by her body. This process is natural and allows the fish to conserve energy and nutrients. However, if a female Betta becomes egg-bound, where the eggs do not get released, it can lead to health issues, including stress or infections. It's essential to provide an appropriate environment and breeding conditions if breeding is intended.
If the female is chubby around the tummy area you could add her but be prepared to remove her if the male gets too boisterous. If he starts building a nest then you know you are in with a chance.
If they are not too old and the female is ready, then they will mate.