Girls, we think it's cystitis. It starts to get upset, I open a diaper…

Girls, we think it's cystitis. It starts to get upset, I open a diaper she pees. Then after some time again the same thing, she pees a little and so on. What should I do? Who has encountered this? At first I thought that she doesn't want to just write in a diaper, although this option is still not excluded because it starts when the diaper fills up, or medium filled