I Have A 5 Yr Old Granddaughter That Was In

I have a 5 yr old granddaughter that was in the local ER on Sunday for what was believed a UTI. She was medicated by an Urgent care. At the ER they drew blood, took stomach xrays and used a catheter for a clean urine catch. All tests came back in the normal range. They put her on Keflex and she tolerated it well sunday and Monday. Monday she developed watery diarrhea and this morning she has a temp of 102.3 under the arm. I gave her 2 tsp of Tylenol. Is this a drug reaction?