Please correct me if I'm wrong but in Japan cross dressing is a minor culture and there are some okama (it's a slang for homosexuality/cross dressing iirc) bars in Japan...Also Ouran High School introduces Haruhi's father as okama btw
But yeah, okama bars are basically gay bars but more shifted towards cross dressing.

It's more common to meet cross dressers than transgenders in Japan I believe.
So in that context, Heidi is most likely a cross dresser ofc unless later chapters defines it otherwise! That'd be p cool tbh

I don't usually comment on things but I just wanted to share a little bit of information that I know of okama in case that people are not aware about this...

Anyways thank you for the upload I really love aniyome!