What Can Be Done To Make The Child Understand That Urination Should Not Be Held ?

my 6 year old niece had been holding in her urine because she said it hurts to pee. when she couldn t hold it in any longer she screamed in agony while peeing. a doctor diagnosed her with a severe infection and gave her antibiotics . she s been taking her medicine for about 4 days now and is much much better, however, she is still afraid to pee and keeps holding it in for long periods of time. when she goes, she admits herself that it doesn t hurt but still, she holds it in until she can barely walk because she is so scared that peeing will hurt! we tried rewarding her if she goes, and everything else we could think of! holding it in for a long time creates a problem in itself right? what would you suggest we do?