Hi kristijames01, I have heard of other problems with a female child a bit older than your step daughter. It was suspected she may have been molested by one of her mothers many boyfriends.
This girl was very neglected and in the end her father fought and one fulltime custody. But perhaps your step daughters personal hygiene is not the best and this may be why she has these sorts of infection. Her mother may not be making her take a bath often enough or helping her wash. Or on the other hand perhaps she has an allergy to the soap or bubble bath she is being washed in? I know that a UTS can be transmitted to your anus so when you are wiping yourself after going to the toilet you have to be careful not to cross the germ to your anus and then transfer it back to your urinary. Sorry for the graphics. The other thing is perhaps her mother is not helping her with applying her cream for the thrush or perhaps she thinks it is gone and stops the cream too soon. Maybe she thinks the daughter is old enough to apply it herself? They may also be stopping any medication for the UTS too soon as well. If she gets another one perhaps a MSU (mid stream urine) test should be done after treatment to ensure the germ is gone. I had a UTS once and it just seemed to keep coming back but I was a grown up. Sometimes children are so involved in playing they dont want to stop to do anything including going to the toilet. Perhaps she has been holding onto her urine and not going, this may cause an infection.
Having said that I would advise this 1. speak with your partner about ANY concerns you may have for his daughter. 2. If you still have any concerns take her to a trusted Doctor and let them know your concerns and have her examined. They should know if anything is not right. Ask your step daughter to wait outside and speak to the Dr on your own and ask them is this normal for her age and why would she get them. You may be concerned about nothing but on the other hand.............It is our job as adults to care and look after children. They rely on us to speak up for them. I really dont know and just stabbing in the dark but one thing is for sure she is a very lucky girl to have a step mum who cares so much about her. Good luck!