Brief Answer:
UTI plus DIarrhea, medications plus something else

Detailed Answer:
Thank you for asking
The symptoms of your wife are because of UTI.. Diarrhea not responding to medications and resolving are likely a correlation with the previous medicines of olmesartan as 1 out of 10 person gets severe diarrhea with the medication.
But there might be some other confounding factors like functional bowel like IBS, an acute gastroenteritis , a food poisoning or any other cause.

Nut shell diarrhea is always one from the following cause
Infection by bacteria (the cause of most types of food poisoning)
Infections by other organisms
Eating foods that upset the digestive system
Allergies to certain foods
Medications
Radiation therapy
Diseases of the intestines (Crohn's disease, ulcerative colitis)
Malabsorption (where the body is unable to adequately absorb certain nutrients from the diet)
Hyperthyroidism
Some cancers
Laxative abuse
Alcohol abuse
Digestive tract surgery
Diabetes
Competitive running

Now whats causing it in your wife's case needs a little correlation. To me medications and associated hidden confounding factor is responsible.

Now the UTI so that is a gift in old age.UTIs / Urinary Tract Infections are a major concern for women and almost 25 to 40 % women have them at a single time amongst all women on dart and every women has the chance of 80 % to get it once in a life. There are above 50 million visits worldwide to the Hospital for this issue and 20 % visits are to the Emergency Departments. Adult age between 20-40 are more prone to this infection as manipulations and coitus resulting in Honey Moon Cystitis (UTI due to Coitus) and pregnancies are on the top, In Old people catheterisation is the major criminal.Its like instilling the organisms which is inevitable, 24 hours stay of catheter inside the Genito Urinary tract makes the likelihood of infection 100 % which means in editable, that is why it is recommended to avoid catheters as much as possible and when necessary intermittent catheterisation should be preferred. In children its mostly because of some anatomical malformations like VUR Vesico Ureteral Reflux or fistulas etc.
Now what makes UTi more troublesome and resistant? so old age, General disability , Hospitalization, Instrumentation and manipulation and interventional procedures in Genito Urinary tract, Renal infections, Stones in kidneys, and Diabetes Mellitus are some common reasons for resilience.
Now lets talk about what we can do to avoid them.
It is said that drinking plenty of water is the best way to get rid of the organisms and clearing the pathway of them. SO drink as much fluid as you can, At least 12 to 16 glasses of water a day.
Then comes the role of hygiene, Front to back unidirectional wiping , using hot saline baths, sits baths, Avoiding unnecessary douchings, Not using Beauty soaps or perfumes down there, Good toilet hygiene, Post coital voiding immediately, avoiding unnecessary manual or digital or lingual manipulation of the area to avoid troubles.
Recently Use of Cranberry juices 10-12 ounces daily work like charm. These juices have proanthracyclins in them which doest allow organisms to stick to the pathway epithelium and thus decrease the predispositions to infections.
Those who have trouble with pain during micturition can get relief from bladder analgesic like Phenazopyridine if Sulfa allergies are not the problem.
Recent use of Intra bladder Instillations of Hyaluronic acids and chondroitin sulfates have proved very efficient.
Rest the antibiotics like quinolones, cephalosporins an. penicillin, sulfonamides and aminoglycosides with other symptomatic treatment is advised after being prescribed. Symptomatic treatment is used like antispasmodics like phloroglucinols or hyoscine etc and simple analgesics like acetaminophen etc suffice.

Nutshell, she needs electrolytes supplementation and assessment of hydration. Continue the BRAT diet, seek a doctor for an alternative Antihypertensive medication. Wait and see is the key and do as directed is the request.

I hope it helps. Take good care of yourself and dont forget to close the discussion please.
I Hope it helps. Take good care of yourself and dont forget to close the discussion please.
May the odds be ever in your favour.
Regards
Khan

---