From what I have read, there are a number of reasons that a post-transplant patient's ferritin level could be high and their platelet count (trombosit) could be low. Those reasons include graft-versus-host disease, inflammation, side effects of drugs, infections, or in the worst case a relapse.
I can understand why you are worried about this. Her doctor may want to run tests to determine the cause, and what can be done about it. But I should mention that one pair of blood tests may not prove that there is a trend. Lab results can be inconsistent, so it may require a few more blood tests over the coming weeks to know if her levels are stable or her counts are really going in the wrong direction.
Has your daughter had a recent bone marrow biopsy test? That can provide a better picture of her bone marrow health than judging by blood counts.