Sadly, you're still going to occasionally have a captive bred with this personality. It just happens. So even just her being the one wild caught with this attitude happens. I have a CBB one just like this.
She's better now, not ready to fly out of the tub for you right away.... But still thinks about it and if you give her enough time, she will. Some are just very defensive.
Short and regular handling sessions are definitely a good idea. You can also try sitting somewhere quiet with her wrapped in a pillow case or a sweater so she can get used to your smell and such.
Tap training like you are right now is basically Switching from the active defense to the more passive defense. So that's not a bad thing. It still is something that could be making her nervous though since she is wild caught.
Just don't expect her to become an animal that you can hand off to anyone to handle. She will most likely always be defensive and will only tolerate handling with you because she'll understand that you don't intend to hurt her.
And by not expecting much, if she DOES turn around and become easily handleable, congrats!
Every snake does have their own personality. So if this is her, just keep her healthy and 'happy'. I've learned the limit for my girl. She's one of 2 spicy defensive BPs I have. Then I have a couple of shy ones and then I have 3 super sweet and interactive ones.