I seriously just smacked my forehead. Why do you have Bettas? Why are you trying to breed them?
First thing is first. Do you buy a car because you drive by it and it looks pretty? No you look at it's price, it's history, you want to know how to keep it in working condition like oil changes, gas, etc.
So why did you just buy these fish without doing your homework. One thing, your female is going to die now from the stress of being with the male. What size container do you have both of them in? Bet you it is less then 5 gallons right? I'm sorry if I am being mean but I have to make sure you understand the reason this is happening is because of you. I am happy though you are using conditional and using blood worms. Those thing you are doing right but you need to do a little more research.
Sadly right now all I can give you for advice is move her into her tank and hope she recovers but it honestly sounds like it is too late. Sorry
Added to your response:
You stated you put her in with the male tank and nothing about removing her. So this is where I was coming from. She is still dieing if she is laying on her side. Taking a fish out of their enviroment and just throwing her into another enviroment and then back to the old enviroment produces a lot of stress. You need to introduce the fish over time and not instantly. You did some research but you need to do more. It's like picking up a picture book of Red Riding Hood for the first time and trying to get the same knowledge of the story without the words.
What size tank do you have her in, how often do you change the water and how much of the water?
Also do you have a heater and filter?
Edited for new details.
Usually you want to have a filter as this builds good baterial to allow for ammonia from quickly building up. It could take as soon as 24 hours for ammonia from uneaten food to reach deadly levels of toxicity. When she doesn't eat her food, do you remove the excess? If not, it is probably why she has been sick. She probably got bloated and stopped eating for a day or 2 and causing the uneaten food to build up faster then normal which inturn cause an ammonia spike. Change 50% of the water now and use a chemical called PRIME (only 2 drops). This is your Declor chemical but it also helps lower ammonia, nitrites and Nitrates.
Generally hobbiest say 5 gallons min for Bettas because a filter can only really work in a 5+ gallon properally. If you don't want to invest in a slightly bigger tank with a filter, I would look into buying the API Ammonia Testing drops so you can check the water every few days to see if your ammonia keeps spiking that way you can adjust how much you feed her and remember to remove anything she doesn't eat. When changing her water weekly, do only 25% at a time as not to cause a tempature spike which can shock her which can easily lead to death.