Ah gotcha.
Not my mum, but my grandma had high aspirations for her own family (was beside herself when my aunt married a posh Navy officer and my dad went to uni, that kind of thing). She always regretted not marrying someone better off although my granddad was lovely. Total Hyacinth Bucket, bless her.
Anyway, she didn't latch onto one family in this way but we would often hear very detailed reports of other, richer families and what they were doing, as though they were close friends, when in fact, she hardly knew them.
I think my dad feels as you suggest, that her own family was never good enough. I know she was proud. She was just an intelligent, ambitious woman kind of stuck in her place- she says she had a place at university but then the war started and she had to work near home. Then she ended up getting married quite soon after the war simply because of the age she was when the war happened.
So, in her case, I feel as though she felt she had not met her own potential and lived it vicariously through those she thought should be her social 'equals' had she had the chance.
Maybe it was similar with your mum, lack of personal fulfillment rather than not appreciating you and any siblings. Shame she let it spill over into this ongoing narrative though, that sounds quite upsetting to have had to listen to all the time.