it sounds like my betta, I suggest stocking up big time on the meds I'm about to tell you, and then use them for the reasons also next to them, main info found at bettatlk.com/
BettaZing
(a great substitute to bettamax - anti parasitic, anti protozoan & anti fungal) Great all around preventative. Very effective against velvet & clamped fins. Use anytime you add new fish or acclimate.
tetracyclin
(antibiotic) Good for bacterial infections
kanamycin
(antibiotic) Good for serious bacterial infection
Ampicillin
(antibiotic) Great for pop-eye and gram positive serious infections
maracin 1 & maracin 2
(anti fungal and antibiotic) OK for mild infections such as slight fin rots, but not very effective for serious stuff.
jungle fungus eliminator
(anti fungal) Great for fungus infections
Another thing is to be sure of what you have; For instance your Velvet seems like you oidint know what it was and the fungus growing is what it actualy was in earlier stages, that is called ICK And it can sometimes be like velvet but they are totaly different illnesses. Ick is sometimes deadly but not always fetal and will sometimes go away on it's own, but thats not likly cause you left it get to the advanced stage and you need fungle infection remover by jungle, Better know as jungle fungus eliminator That you can find at any petstore with fish.
Velvet IS NOT DEADLY its something that happends and inless the betta is more then 5 years old, you have more chances of it going away on it's own in warm water with no meds, if it is older then five it still cant die from it no matter how late you catch it, for instance it can have a hole in it's head and still recover 100% and that is in the final stage and the betta is sideways in the tank from the velvet, but velvet is a Bacterial infection and not a fungle infection, to get rid of it in any case you can use as shown above for minor bacterial infection to serios infections. However do not use it till you know thats what you have, the best way to know what you have is to shine a bright 75 watt right at the scals of betty, watch her swim and if a Dark Pale Purple spot is anywhere on her body that shines, she has it, if it's gold go strait to SERIOS bacterial infection medication. And as soon as possable for that is a deadly internal bacteria and the golden flects shows it's in advanced stages.
But you sound to only have Ick.. And for that it's very easy, just stay calm =3 do a good water change from the meds she had before" DO NOT PLACE IN THE MEDICATED LIQUID" cause the fungle and bacterial meds will interact with eachother and do nothing, the water will become nutral again within a few days and you would have done nothing =/ only put it in after you put her in a cup, rinse the tank in hot water, dry with a live sponge and refill. Then place the jungle fungus eliminator right into the water and let it filter for the derected deration of time as the bottle calls for, then get her out of the medicated water with a net or your palm ( for they live five minutes Easily out of water and the ick wont hurt you) and put her deep into the clean fugus filtered aquarium.
Slowly raise the heat afterward to about 82 and though it is hot, the fungus will fall off from the jungle fungus eliminator and then the heat will burn it alive without harming your betta, then about three days laiter do a 25% water change and put aquarium salt in the water =3 after that continue with aquarium salt at every water change and she should be a-okay in the first 72 hours of treatment ^_^..
Hope that will help you, and try to identafy about betta desease a little more before you medicate a betta for any other deseases, cause sometimes if she did have golden flick, what you just put in may have harmed her, cause it actualy helps that kind of bacteria thrive. And if it was TB, you could end up with a dead betta within 13 hours time cause that only activates the active TB cells.