Many kitchens are laid out around one person's reach, and most of the things she uses every day may sit higher or lower than her hands can comfortably go. You can fix much of that without a contractor. The work is measurement and a short list. If you cannot be there, you can do the first half on a video call with someone local holding the tape.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Start with her reach, not the shelf
Ask her to stand where she usually stands at the counter and reach forward with her arm relaxed. Note the height her hand reaches comfortably, then the height she reaches when she has to stretch. Write both numbers down. Do not use the top shelf or your own reach as the standard, because both will overstate what she can use safely.
List what she touches every day
Ask for the items she uses at least once a day: the mug, the cereal, the plates, the pan, the kettle, the bread. Skip the holiday serving dish. Put each item on a list with the cabinet or shelf it lives on now and that shelf's height. Anything above her comfortable reach, or so low she has to bend deeply to reach it, is a candidate to move.
Move first, buy second
In most homes the fix is moving things, not installing anything. Put the daily plates and cups at the height of her comfortable reach. Move heavy pots low, where she can slide them out rather than lift them. Keep the things she uses twice a year high, where they belong. Before you buy a rolling cart or a step stool, check whether a rearrangement solves the problem. A step stool can itself be a fall risk, so it should not replace moving the item.
What to check before you buy any new unit
If rearranging is not enough, compare the depth of any new unit against the counter, the swing of the cabinet door, and whether the new shelf stays in place when she grips it. Ask the installer to show you the load rating in writing and to confirm the unit is fixed to wall studs, not drywall alone. A unit that wobbles under a hand is worse than no unit.
If you need someone local to hold the tape or check the install, the Local Help for a St. Louis Parent page lists the kinds of people who can do that work.
Tonight
Ask someone local to take five photos of the kitchen from where she stands at the counter. Write the list of daily items with their current heights. Move only the three items she uses most, then ask her how it felt to reach them the next morning.
What to take to the doctor
If reaching overhead or bending to low cabinets leaves her unsteady, short of breath, or in pain, write down what she was reaching for and what happened. Those notes help her doctor decide what needs a closer look. Bring the list of items you moved so the doctor is working from the real setup at home.