I think you should keep it simple in the beginning.

You can add in the Benfotiamine, as it appears to be really safe.
Some people have errors in thiamine metabolism. Start at 150mg which is conservative. (you can use regular thiamine if that is easier to obtain). Many people on this forum do well with thiamine/benfotiamine.

But give the B12 3months to work. Oral just gives 13mcg/1000mcg dose which isn't alot.

The body will pick and choose where to send the B12...it has priorities that haven't been really researched. So the onset of supplementing is not fast, and unpredictable.

If she did 5mg once a day on an empty stomach, the initial response would be faster.
Before any retesting, stop the B12 about a week before, so a more realistic result is measured. You don't want any false elevations to be revealed as those are confusing.
Once a level of 1000pg/ml is reached you can back down to 1000mcg a day if you choose.

If you introduce too many supplements at once, it can be difficult to figure out which one(s) are working for you.