Ok Serious Question Time, I've Got This Friend And They Want To Transition. I Asked Why And They Said

Ok serious question time, I've got this friend and they want to transition. I asked why and they said that it was to get their partner to like them more. Their partner has a weird thing for trans people and wanted them to transition because "They would look so much better if they were trans". Their partner is really horrible and has been very manipulative in the past so my friend doing stuff they don't like to please them is something that happens a lot. We try to get them to break up with their partner but it's to no luck and most of my friends don't talk to them anymore because of how rude they can get when you say something about their partner. I told them that transitioning just to please someone else is a bad idea and unhealthy but they called me transphobic and that "I haven't let my past self go". Of course I don't have any problem with transitioning but when I first met my best friend (This is a different friend then the one I was previously talking about), bird had neo pronouns and as someone who didn't speak English originally, it was hard to learn the language and kinda break the language rules at the same time so I ended up just calling bird "she" and bird never corrected me even though they had a problem with it. We both sorted out that issue a while ago but I need to know, was It wrong to question my friend about their transition? I really know nothing about trans stuff since the first time I heard of that was when I first met my best friend. Please don't be mean because I really don't know if I was wrong or not.

(Also btw I call my best friend "they" sometimes because that's what bird was fine with me calling them when I was learning English and it just stuck)