Female with male betta???

If you do, it's possible they could mate in which case you'll have fry on your hands. Are you prepared to care for the resulting offspring ? If they are not ready to mate they will fight and it's very likely you'll end up with a dead fish. You'll also have to remove the female once they have mated as the male most likely won't tolerate her presence while he carefully guards the nest.

So no, I'd say it's not realistic long term. If your ultimate goal is breeding, then I would suggest doing some reading on bettas.

That is pretty good advice. The best way to keep male and female bettas together is to do so in a large planted tank with at least 3-4 females per male. But realistically it generally does not work well and a 5 is just plain too small.

it isnt generally advisable to put females and males in the same tank. even when breeding they are separated until the bubblenest is complete and the female is ready etc. otherwise, the male and female will fight constantly. you are better off with either one male or one female in your tank.

Housing a male and female betta together is fine as long as you have enough room and enough hiding places. Since bettas are such a generally aggressive species, they tend to establish their own territories, and they like to be left alone. So in such a small tank, i.e. anything under 10 gallons, it's definitely not a good idea. The female will tear the male to pieces, since she doesn't have enough space to hide from his advances. You'll end up with a shredded male and an angry female.
If you have enough room, though, they will get along quite well. I have a group of females with a plakat male in my 60 gallon, and I've never had any problems. I've had other pairs in other tanks, as well, and under 10 gallons things get nasty, but above that they do very well.

It really depends on the individual personality of each betta.

Most male bettas will attack another betta, male or female and fight to the death every chance they get. Some males may chase a little bit, but won't kill unless they have to. And on the very rare occasion, you may find a male betta who is peaceful and mellow, ignoring all other bettas.

Females can be just as unpredictable.

It is possible to keep multiple bettas in 1 tank, if the tank is large enough and has plenty of hiding. 5 gallons can't accoplish this. When they are kept together is is usually best to keep at least 3-4 females and 1 male so the male has several targets rather than just one female to pick on. This keeps the females safe. However it is possible that the females may gang up on the male and kill him, so it is always important to have a back-up plan with bettas because they are so unpredictable.

I have a male and female in my 46g community thanks to my girlfriend and they get along great. If I had my way id have no bettas in my big tank but after seeing how much they enjoy all the room I cant bring myself to put them in smaller tanks.

On a side note this same girlfriend tried putting the female in with our monster betta in the 5g and that wasnt working at all hence how I ended up with her in my 46g