I can't remember precisely what your wording was, only the sentiment it expressed, and I believe that sentiment was along the lines of "she was born a man".

The trans experience (in fact, the experience of gender for any human being) is varied, personal and unique to each person, and as such there is nobody on this earth who can say what gender she was when she was younger is her.

Doctors and other medical professionals could have taken a look at what sex characteristics she exhibited at birth, and decided that mostly fits into the bucket of "male". For the majority of people gender and sex line up neatly, and as such the two are often conflated as being the same thing.

To assert that she was "born a man" you must make this incorrect assumption that gender and sex assignment are the same concepts - but this is false (and harmful to propagate)

She was assigned male at birth (presumably) and she may have experienced gender as a boy/man for quite some time growing up, or she may have always felt something wasn't quite righ, or she might have had some completely unique experience of gender that I could never even dream up as an example for you. The only person who can say if she was born a man is her. Doctors can say if she was born with male sex characteristics.

I know I'm repeating myself somewhat, but I hope this helps.

Edit: I knew I'd forget something as well.

Even if your sentiment had been "she was born a male" (which, god, you'd have to know her quite privately to be able to know that!), its not a particularly useful thing to bring to the conversation, and allusions to trans folks expressed sex characteristics that may not align with the gender they identify with is generally a bit of a dick move. Like a more intense version of telling a cis woman they have a manly face, I guess. And, a more appropriate way of expressing it if it is relevant to the conversation, is simply, "assigned male at birth".

Apologies I don't always have a ton of time to explain to everyone exactly what they did wrong. In this case you entered a thread about minorities and made an assertion about their lives to challenge a narrative they presented. If you had educated yourself on this issue first, you would quickly find this is a narrative often imposed on transgender individuals, one which directly effects their lives and one in which the person being discriminated against is often having to explain to the majority why their assumption is incorrect and how they are being harmed by it. If you are not the person being effected by a system you need to educate yourself before engaging with someone who is effected by the system. If your goal is to come and gather info, you should be on your best behavior- this means thanking them for engaging with you, realizing you're asking for their valuable time and energy and experience, asking questions in a very polite manner, and never attacking or making any assumptions about them.

With that being said, the general statement asserting someones sex or gender was an assumption about their life. You don't know what their legal papers say or even what country they are from. You definitely do not know their genetic information and it seems like you're not particularly knowledgeable about intersex individuals or the nuances of genetics and expression. If your intention was to reflect upon what society likely did to this person, the language needs to reflect that- for example you can state that they likely received a gender on their paperwork because a doctor decided it based primarily on the person's external appearance at time of birth. That's a very different statement from 'they are genetically this gender/sex'.