I would recommend that she mix some bleach, vinegar, and ammonia into a large aluminum pan, and just before she puts it in the oven for the night spray some Easy-Off Oven Cleaner into the mix.
You know, when I was young, I used to mix bleach and ammonia for cleaning.
Having grown up around hospitals, I liked the idea of antiseptic, and thought this would be a good mix, getting rid of germs, and not just odor.
Nothing bad ever happened, but I guess it's not a good idea.
And of course, now that I have all these cats, I have to be more careful about mixing chemicals.