This story is not unique. I have seen several slightly similar stories online, though of course nothing online can be verified or falsified.
One story I remember was about a transitioning male who wanted her/their niece to go for a shared bra shopping and makeup shopping trip, with awkward questions about the teen girl's body and a request to be in the same cubicle while trying things on. The niece felt uncomfortable with it and some other things of a similar nature.
These are not things that young female relatives should be asked to participate in, just as it would not be appropriate for a transitioning adult female to ask his/their nephew to go on an underwear shopping trip with similar features otherwise.