You don't have a verb in that phrase and you can't use -law' on a noun. I'm guessing that you mistakenly thought that tlhoqtlhal was a verb meaning "to do a favor" instead of the noun "a favor"? Unfortunately I still can't quite figure out what you meant. Tell us what you thought that meant in English and we can help you.
I was trying to say "Mara seems to favor her big toe," thinking that tlhoqtlhal was a verb meaning "to favor (something)." I read the description on hol.kag.org, and misinterpreted the "The recipient of the favor is marked with -vaD" to mean that it was a quirk of the language that the object of tlhoqtlhal was marked with -vaD. Is there any way to say what I intended?
You could use the verb maS meaning prefer. Or you can use the words in the course to say that she customarily uses her big toe.
In English to favour a limb can mean to use it less, or is that only with horses? A horse that is favouring a leg appears to be lame in that leg.