My thoughts are you are probably overthinking this.
An 18 year old requesting a VV to visit her Mother is very different to the usual applications asked about on here where it’s commonly a short relationship so I doubt a reason to return would be as stringent in your case. Obviously address it but as you know, tell the truth and you don’t need to mention the details of her upbringing.
You will have a birth certificate in black and white as proof of a relationship, possibly proof of money sent but with the age of the daughter and the fact it is a VV a Khor Por 14 wouldn’t be expected.
Your wife’s history on visas also shows you don’t abuse the system which is what they’re looking for.