Frozen foods are great, IHMO. They don't carry the risk of parasites that live foods have while still having more "life-like" properties than freeze-dried. And, while freeze dried foods have come a long way and hold much more nutrients than ever before, they can lose nutrients in the freeze-drying process (depending on brands, might be alot, might be minimal).
You can now get minicubes for smaller tanks and/or smaller fish. It's still going to be more than what a single betta will eat, but I just defrost the cube, feed what my smaller fish will eat, and then give the rest to my other community tanks.
As for the allergies, yes, lots of people can be allergic to bloodworms. This is mainly a sneezing, runny nose thing, but some people have worse reactions. I believe that frozen bloodworms are less likely to be a problem because they don't throw particles into the air like freeze-dried ones can. One way to minimize reactions with freeze-dried ones is to use tweezers to feed the fish instead of picking them out by hand. You can also wear gloves and/or a face mask if you are really committed, but I'd try frozen or other foods instead if it's going to be a problem. There's really a lot of foods to choose from these days, so if she does have a reaction, I would just use something else.
