No, feeding only brine shrimp is like feeding only candy flavored laxatives to a child.
The best way to get her to eat is to fast her for a few more days, then try to feed her a healthier food. If she still won't eat it, fast her for a few more days. Eventually, she will get hungry enough to eat what's good for her.
Don't worry, healthy Betta fish can go 2 weeks (sometimes more) without food - if she knows that you will feed her her candy, she won't eat the other stuff, so don't do it even if she looks at you with the pitiful begging looks.