The manager isn't quoting the property code law per se, she's relating it to the Board in her own words and then sometimes explains what it means when asked. Are you saying that she shouldn't be explaining it?
Yes, I am. If she is in the employ of the HOA and is giving interpretations of statutes (for one), then she is taking compensation (money) for legal advice. She is practicing law without a license, in violation of the law. See https://statutes.capitol.texas.gov/?tab=1&code=GV&chapter=GV.81&artSec=81.102
Personally, I don't think it is unreasonable to expect an HOA management company representative to have a working knowledge of, at least, the state HOA property code laws.
I would say it is quite reasonable for a HOA MC to have some knowledge of the law. The problem is when they take this knowledge and behave as an attorney would behave, and while being paid for this behavior.
If she knows about a particular law that the BOD may be unknowingly violating by a decision they make, isn't she culpable in that violation if she doesn't inform the BOD of that law?
No. I think what you are proposing is that the MC may be committing some flavor of malpractice by withholding her knowledge of the law.
As long as she does not give legal advice, she cannot commit malpractice.
Furthermore, if she does give legal advice, then in addition to violating state law, she might very well be committing an ethical violation of her regulating authority's rules of ethics. For example, see https://www.caionline.org/getmedia/f3e4377c-db51-42c1-8303-e5a7f23af297/ethics_code.pdf , page 4, part D 4. From the latter:
"managers shall not provide legal, accounting, insurance, or engineering advice and must leave such advice to the
appropriate, licensed professionals, including lawyers, insurance, engineers, and accountants."
What the manager is supposed to do is advise that the HOA Board consult an attorney.