ط makes the same /t/ sound as ت in modern Urdu. Same as the sad/zad pair, this is an Arabic-loanword spelling distinction, not a sound distinction. Children learn through reading which words use ط and which use ت. Common Arabic-origin words tend to use ط: طبیب (tabeeb, doctor), طالب (taalib, student). Indic-origin words use ت. Stroke timings approximate.

When she writes طالب علم correctly with ط not ت, that is real knowledge of Urdu's history showing up. Name that.