How high in her blood pressure? Is she taking medication to bring it down?
Weight loss would probably help tremendously in getting it lower, plus being 300 lbs is a strain on her organs and heart.
The best thing would be for her to see a nutritionist (she can ask her doctor to recommend one) and get on a medically supervised eating program. Stay away from pills, crash diets, and fads.
Good luck to your mom..
Slow but sure weight loss efforts are long lasting. A quick fix (eg. crash dieting) while emotionally satisfying in the moment, is almost guaranteed to come back and bite you big time in the form of regaining the weight and then some (a miserable experience).
I think the starting point is when she wants to lose weight badly enough to do something effective and safe about that. eg. If as is likely she's been using food for comfort and entertainment, then she probably needs to change her attitude to just thinking of food as nutrition while choosing healthier foods (and no longer stocking her kitchen / fridge with poor to bad food and drink choices).
Dropping convenience, processed and junk foods and switching to homecooking, smaller forks & spoons & bowls (to slow down eating so that I'm better aware of having satisfied my hunger), has worked well for me. A lot of people eat until they're feeling full, which is fine if they're burning it off and not gaining weight that way but, it's just too much for most people with a weight problem who, I think, ought to just eat slowly at meals until they're no longer hungry. And have some healthy snacks (apples, carrot sticks, etc.) at hand in case they're hungry between meals.
Hi, just wanted to say real fast that my sister AND my husband have both been diagnosed with high blood pressure in the past. Additionally, both of them were found to have completely normal blood pressure once the correct size blood pressure cuff was used on them when measuring blood pressure.... Just a thought! If you're not sure why you have high blood pressure, and are otherwise healthy, ask your doctor/nurse if they could try a more appropriate size cuff (for my sister and husband, they needed a bigger size cuff) and see if that changes results.