1: Goldfish shouldnt be kept in the same tank as Bettas/Tetras because of the amount of waste that goldfish produce, as well as the need for different temperature requirements. I suggest you return the goldfish to your LFS.
2: Female bettas need to be kept either alone, or in groups of 3+ to spread out aggression. The larger the number (without overstocking), the more spread out aggression will be, and the happier they'll be. Personally, I recommend a minimum group of 4.
3: Tetras are a schooling fish that require a group of 6 or more. Depending on the type of tetra, you may find them incompatible with the bettas as some tetras can be quite nippy.
4: Tanks with female bettas need to have a lot of hiding spots for them. 1 hiding spot per betta is a great rule of thumb on this, but a couple extra hiding spots is always a good idea. This way the fish can get "out of sight" from each other, allowing them to get away from the aggression and bullying.
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Edit: It is possible to keep females together peacefully in a tank. I have a 15 gallon female betta sorority tank with six female bettas (soon t be adding 2 more). They've been together for ~8 months, and while I had aggression in the beginning while they worked out a pecking order, they're all perfectly healthy and friendly now. They even swim around together and "play" together in the plants.