I Honestly Don't Know The Answer To This

The trans girl wouldn't be a boy at all so no. Tne cishet would have to be at least bi.

Transboy: ftm. So you would have to have attraction to men..

Whats your gender and other attractions?

So you're bi.

Nah, It would be a lesbian relationship

No the « straight » girl isn’t straight. A possibility is that she is actually demi and is attracted to the person rather than the gender

Found a comic quite similar to this

Thanks for clearing that up. This was just a random thought I had.

me: its lesbian
also me: what if the straight girl decides to come out as trans-male then its a straight/bi/demi relationship

no. it could be any sexuality/romantic orientation except straight

I think they would still be straight, because I had someone in my school who was a lesbian date a trans male (the guy was biologically female, but identified as male). This technically would make it a "straight couple" but they still dated each other since she was lesbian. She wasn't bi or pan, she told me that once as well. So yeah, from this experience I would conclude that the straight girl still is straight, since sexual attraction to the trans girl would still exist due to her having the same body as before the change.