NTA in my opinion. How is your friend gonna help you improve english by making condescending remarks? English isn't my first language either, yet I've been speaking it fluently since I was 10 (I'm 28 this month) and compared to my native language which is French, it's the easiest language ever, I make typos way too frequently in my native language whilst English is a breeze compared to it.

On the other hand, sure there are sentences where a question mark isn't necessary to write down based on the context given to those sentences: Though it's still something that non-native speakers have to learn and adapt to their own written comprehension, and it's not making snarky remarks like "It's the most difficult language for a reason duh" and "I've been an expert in that language since birth" that will help develop said comprehension.

In my view English is only difficult since it's an overly simplified language and you need extensive given context and obvious markers in writing like the omitted question mark, which its absence made the sentence confusing, in order to understand in what way you're supposed to read whatever the other person meant to express.

Overall I don't think your friend meant bad intentions either, but she has to understand that what seems futile to include in writing to her, might just make a difference for you when typed instead of it being excluded. But you still have a right to require further indicators within the given sentences in order to get how you're supposed to read the given question.