"bint" can mean both "daughter" and "girl," but "ibn" can only mean "son," by the way. Also, ابن is one of ten nouns in Arabic (not derived from verbs that is) that start with a consonant cluster. Since this is not allowed at the beginning of an utterance, we add an 2i- sound at the beginning of the word, but only if it's the first word of the utterence. That's the sound represented by the alif without the hamza at the start of the word. Otherwise, that alif is silent. Four of the ten words aren't ones you're likely to encounter in your preliminary interactions with Arabic, but the common ones are: ابن ابنة (son, daughter), اثنان اثنتان (two [masculine], two [feminine]), اسم (name), and امرأة (woman), for a total of six words.
Yes, you're right! But as I stated in the original comment, this list is only supposed to include nouns that are not derived from verbs. The definite article is, well, an article, so it's not part of this list. The whole list is much bigger actually, once you figure verbs into the equation.
Just to clarify, I'm not interested what books claim. Language is what people use, not what scholars invent. In actual usage, بنت appears in Google searches about 20 times more than ابنة. As you can see, there is not one single country on Earth that used ابنة even close to as much as بنت, let alone more. https://trends.google.com/trends/explore?date=all&q=%D8%A8%D9%86%D8%AA,%D8%A7%D8%A8%D9%86%D8%A9
Than you gentleman or lady for the statistics. I see your perspective. I do not look at how books use language as well since I have said I live through Arabic in my every day life. My main point is that if you are looking for use then you will see "bint". However, you should distinguish between spoken Arabic and Standard Arabic (the Arabic that we learn at school and that we use as a form of newspapers and academia). Therefore, the graph you have shown does not shown clearly which kind of Arabic is tackled. In Arabic countries, if you say you are learning Arabic, we are looking for the official one, the one that is used in official settings and is a direct descendent from Classical Arabic. However, if you talk about Spoken Arabic, then that's a different matter and dialects are so different from each other especially if you go from the North of Africa (e.g. Morocco where I live) to the Middle East. Either way, whatever you choose to learn the important thing is you have fun and manage to use the language. To clarify again, the graph shows dialects and in here when you say you learn Arabic, you learn Standard Arabic, which is more like the version of Standard English instead of learning American English and so on. :)
Regardless, I am happy that people are learning Arabic. It's such a beautiful language, and I just hope one day Duo actually teaching THE Arabic and not just a dialectal one, which does not really show how elegant it is. :) Thank you for your stop and have a lovely day human :)