Ignore the stupid and be fair but firm.
Honestly I would really suggest a trainer.
I am assuming both are young and a horse straight off the track is a BAD match for a newbie, let alone a nervous newbie. Also TBs tend to be like that.
Please get some hands on help, doesn't even need to be a trainer, do you have an experienced friend?
Personally I don't CARE if the horse acts stupid. They either get ignored or reprimanded then we move on with life. They learn it's not worth it and stop on their own. If the horse has genuine issues with correction I make a point to go nice and slow but will still correct.
That said the "not caring" comes from years of experience and from me being comfortable handling and being around horses, reading their body language, knowing what to do etc etc AND also knowing how to handle "if things go wrong" it's also partially a mental trick, just go "in the zone". If you are calm and confident the horse will be.
I don't expect you to think like this though, while you do need to work on that at the same time you don't want to ignore things, obviously that could end very badly!
Again, I STRONGLY suggest hands on help.
Not sure it matters atm but is your mare actually spooky or just being a brat? I'm guessing it may be the latter in which case all the more reason to "crack down". If she is genuinely spooky (say you shout and yank the lead and she bolts backward terrified AND is actually terrified and not just throwing a fit) then I would say to be less dramatic in your corrections, clearly she doesn't need that and you want her to trust you, and also to work on desensitizing her to your "normal" body language.
There is usually a cause if the horse is way overly sensitive (poor handling, hot food, etc). I knew a mare who would bolt backwards if you did what I just described. However, if I needed to correct her I would correct her the same way (though "softly" but I would do the same thing) AND at the same time if I reached up in the air without meaning and saw her throw her head up with that look I would just make a point of throwing my arms around "aimlessly" until she got over it. She needed to figure out there was a difference between body language and me just moving!!
FWIW this mare was NOT abused (I would do things very differently) and was simply overreacting, she was not genuinely afraid. I also never had this issue when I first met her, it developed through poor management. Just an example of something I would do and sort of a "give and take", depending on the horse and the situation I would handle things differently, possibly very.