I think what your mother said is quite fascinating on all sorts of levels.
I would want to know the answers to three questions.
- What is this "it" that women have ruined?
- When did they ruin it? There appears to be a chronology date element to your mother's comment: 'the problem .. today', and I think it is important to define the chronological parameters of "today".
- And what is "behaving like men"? How do we identify it?
The most interesting aspect, of course, is the "behaving like men", which begs the primary question: how do men behave? Until you and your mother can agree on a set of actions that describe men's behaviour, you don't have a set of values to apply to women's behaviour in order to identify it as "men's behaviour."
However, to use a bit of media and popular culture short-hand, "behaving like men" appears to mean the following: getting drunk, being aggressive, being sexually assertive, working (particularly when a woman has a family).
Now regardless of whether you can describe this as co-opted "men's behaviour" (which is an enormous debate in itself), I think it is quicker to allow the chronological aspect of your mother's comment to come into play -- because this "male" behaviour has ruined something in, what seems to be, the recent past. So I think it is fair to suggest that the ruination of the something has occurred in the last 100 years.
And, immediately, we run into a problem because women have been getting drunk, being aggressive, being sexually assertive, working (particularly when they have a family) in these isles for time immemorial.
Britain has seen centuries of almost constant intoxication amongst women of all classes (fermented drinks, Gin Lane, laudanum grains, Valium), episodes of public aggression (the mill moll urban riots in 19th century Manchester), and centuries of mothers working in mills, factories, shops, down mines and on farms with either their children working alongside them or left at home with another child. Indeed, in the medieval period, women were seen as the sexual rapacious sex (the Wife of Bath was not an outlier at the time), and that perspective only started to change in the late 18th century.
So if women behaving in this way ruins something, that something must have been ruined for centuries -- so it cannot be the source of the recently-ruined "it" that your mother mentions.
Hand on heart, I wouldn't be so harsh on your mother. She has been infected with a meme that I call "Peter Hitchenism": the belief that every women, prior to about 1970, lived in a kind of "angel in the house" haze and none of them went out to work.