Ok haha13, here's some information for you. I generally try to refrain from giving any specific medical advice because it would be to a patient that isn't one of mines, and I don't have all the appropriate information about them to make all my decisions with. Any specific questions should be directed to the healthcare professionals taking care of your mom. However, here are some suggestions, just by looking at the general information you posted.
First off, find out how high your mom's blood pressure is. If it's consistently over 140/90 it is considered normally high, but if you're looking at like 180/90 or something like that then that'd be pretty dangerously high. High blood pressure may cause headaches also because of the extra pressure pushing outwards on the blood vessels in the brain pressing on pain receptors in the brain (sort of like a migraine headache). Nausea from things like migraine headaches can be very common as well, just because of how bad the pain is.
Isoniazid can sometimes cause an increase in blood pressure because it has a little bit of what's called Monoamine Oxidase Inhibitory activity. (MAO-I). This basically blocks the breakdown of things like Tyramine which we find in lots of foods like pickled foods, smoked foods, cheeses, alcohol, chocolate, etc. If you're not breaking down Tyramine normally, it can lead to a push/increase in norepinephrine leading to a spike in blood pressure.
The MAO-I effect of isoniazid isn't really huge, but if your mom is having symptoms, she would likely benefit from cutting out or down on Tyramine rich foods. Google a list of Tyramine rich foods, and experiment by having her cut down on eating those things as much as she can and see if she feels better. Monitor her blood pressure during this time, and see if things become controlled again.
Plus also, during this time when we're trying to get her blood pressure down, have her cut down or out caffeine (i.e. tea, coffee, cola), and reduce salt intake. All the usual high blood pressure precautions for the time being, to see if it will help.
Anyways, these are merely suggestions, and not to be taken as definitive medical advice, given the lack of information about your mom that I have.
Best of luck
