If it's a fair and reasonable point, and I actually agree with her after a quick self-reflection, I'll say as much. Especially in an LTR or with a plate I respect.
Most people (and not just women) who begin to argue get caught off guard when you sincerely agree with them -- it disarms them. It's when you try to defend, explain, rationalize, or minimize your behaviour that you exacerbate the situation.
Everyone makes mistakes and no one is ever always acting as the best version of themselves -- we all have been at various points in our lives needlessly rude, inconsiderate, extraordinarily selfish, and have been in the wrong. I don't think avoiding genuine acknowledgment or avoiding taking responsibility for these shortcomings is the optimal path to take, simply because it's a female pointing it out...
Yes, we all know women can be emotional and that they can whine, b!tch, nag, throw sh!t tests around, and get on a man's case for just about anything (and many times it's just a fleeting mood that has nothing to do with what she's actually b!tching about)... but when you're truly in the wrong... and someone's criticism has merit, I think it's philosophically consistent to acknowledge it as if it were coming from your best friend. Yes, you'll have to drop your ego in order to do it.
There's nothing wrong with acknowledging that a criticism may have some truth to it. We often criticize women for their sh!t on this forum but some of us like to think we are flawless and that we are above hearing it from a woman just because it's coming from a woman...
That being said, if you truly agreed with a girl's criticism, and you took responsibility for your shortcoming, and she CONTINUES to get on your case.... well, that's a different situation... and you should remove yourself from the situation by either offering & deferring the conversation when you're both in a more civil mood, or by getting the women out of your life (Why the fvck would you keep an insistently argumentative person in your life?).
Sure, you can be passive aggressiveness, use game techniques and witty responses, and it may allow you to navigate the immediate situation, but these aren't long term solutions, specifically in LTRs. Also, if you are constantly being nagged by a particular chick, you should question why you are keeping her around -- she's likely low value, and if she is indeed low value, you may need to even question you're own value since you're attracting and hanging on to low-esteem women.
Finally, I'd stress that acknowledging & agreeing with criticism, and taking responsibility for it, does NOT mean you should offer an apology. You can admit you were wrong (or at least, that someone's criticism has truth to it) without having to apologize. There are some cases where an apology may be necessary, but not always. Don't apologize if you're not genuinely sorry.
Men don't run into problems when they concede a woman may have a point, instead they run into problems when they KEEP women who constantly nag at them in their life and either a) always apologize and accommodate to avoid future criticism, or b) always feed the argumentative fire via justifying, defending, blaming, fighting back, or minimizing.