Good morning, because TMAO is a fairly new discovery in the health field with helping to identify risks for coronary disease, there isn’t much I can find on what’s considered “normal” values. It looks as though Cleveland Clinic was instrumental in the research and I’ve found several articles from them about TMAO. https://www.clevelandheartlab.com/blog/horizons-tmao-testing-a-new-way-to-assess-heart-attack-and-stroke-risk/

Below is an excerpt from Cleveland Clinic’s site regarding: Blood Tests to Determine Risk of Coronary Artery Disease. This gives the normal blood ranges for various tests associated with diagnosing coronary issues.
(here’s the link to the full article. https://my.clevelandclinic.org/health/diagnostics/16792-blood-tests-to-determine-risk-of-coronary-artery-disease)
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The excerpt:
“Trimethylamine N-oxide (TMAO)
Why is the trimethylamine N-oxide (TMAO) test important?
Comes from bacteria in your gut.
High levels are found in meat, eggs and dairy foods.
Taking choine, lecithin, L-carnitine and other supplements can cause high levels of TMAO.
High levels in the blood increase the risk of heart disease, heart attack, stroke and clogged arteries (atherosclerosis).
If your levels are high, your doctor will likely be aggressive to lower your LDL and other risk factors, have you take low-dose aspirin twice a day, and have you follow a Mediterranean diet.
Levels:

Low risk: Less than 6.2 uM
Intermediate Risk: 6.2 - 9.9 uM
High risk: 10.0 uM or higher”
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A little more information on TMAO in case you’re interested. https://labs.selfdecode.com/blog/tmao/

And another article on TMAO and how to reduce the blood levels.
https://nutritionfacts.org/2021/03/02/how-to-reduce-your-tmao-levels/
If your wife’s level has increased substantially, along with her triglycerides it might be worth a little more research to see if a diet change is necessary with regards to some of the foods mentioned in the information on how to reduce those levels. If her other blood numbers are fine, then it might just mean a change in diet.
Has she had a calcium score test? Where her cholesterol levels good? Does she have any coronary issues or was this just routine bloodwork?