UTI is caused by bacteria. How the bacteria gets inside her urinary tract can be any of a number of reasons.
Most likely scenario is you caused it during sex. Enda upimwe.
But it could really be anything, even food. You know you Somalis with your poor food hygiene.
When you are 5 people eating from the same plate with your hands, how do I know the other four people washed their hands properly after using the loo? Especially after washing their egestion ends in the halal way?