Concerned about my mums behaviour

[Ladybirdbutton]

To cut a long story short she seems to be hugely attention seeking towards men, her own son in law in particular.
she has 3 daughters, I’m the eldest, middle daughter sees what I see, youngest daughter isn’t concerned by our mums behaviour. We’re all in relationships, youngest recently married.
our mum will flirt openly with my brother in law (youngest sisters husband) whenever he visits. Today we are having a family day on the garden with a bbq and pool for the kids. My mother hung out her washing including about 10 pairs of ‘sexy’ underwear and made a rude remark about them to my brother in law so he would look at them.
she has been very touchy feely with him too. He seems uncomfortable but my youngest sister isn’t reacting negatively but laughs.
second sister told mum to stop as the kids will see and she got very defensive and angry that she’s having fun and isn’t hurting anyone.
this isn’t the first time. She apparently tried it on with her own sisters husband many years ago, although her sister passed away so never confirmed. She doesn’t seem to accept any boundaries and would clearly be up for an affair if brother in law was. Hanging the underwear out for the whole family (and neighbours) to see is the final straw, it’s not just a basic pair of briefs it’s Ann summers style stuff. I don’t know how to approach the situation or if I should just ignore it and avoid any family gatherings from now on. I’m appalled by how she acts in general and always assume when we go out that she’d ask for a married man’s number or something really cringe. Without it causing offence to anyone could this be a ‘midlife crisis’ or a sign of a health issue or am I just clutching at straws and she’s crossing a thick line by doing this regardless?
she’s been single for 5 years so perhaps yearning for a man but this isn’t the way to go about it, my sister and I are sitting here waiting for a scene as since I started typing she’s mentioned how so and so across the road must have a large penis due to the way he walks and it’s clear some of the adults are shocked and annoyed.

Has she always been like this or has could some kind of event made her lose her inhibition?

It sounds like your brother in law needs to say something to be honest. He didn't have to put up with this.

I'd have said that maybe she has a recent condition involving lack of inhibition (early dementia/mild stroke/brain tumour) but if you say she was like this many years ago, I suppose that's less likely

She’s mid 50s so I’d assume she’s quite young to be showing signs of dementia or such? I know it can begin at any age though. She was ‘wild’ in her younger years so it isn’t unknown for her to have a lot of men interested in her, but I think doing this with her son in law and basically any man who crosses her path is desperate and sickening to watch. She once commented she could do better in a bar than youngest sister as she’s overweight but mum is size 6 and looks good for her age, almost like competing with her daughters yet none of us are competing back. Fear of getting older? We’re going to try and get brother in law alone to talk about it but sister made a good point that for all we know he is ‘up for it’ and why she does it repeatedly as he doesn’t say stop

Could be a number of things. Trauma, neurological, narcissism. Just ask her what's going on when she acts like. She may be defensive but you can't tip toe around it.

I would say her behaviour possibly stems from her early years, something has made her believe her primary value is her sexuality. Does she work OP? Have any hobbies or skills? The competing with her daughters and inappropriate behaviour could be her fear of her visual appeal and attractiveness fading. It could all stem down to insecurity. I agree you need to deal with it though.

Oh god this is awful. Some women are like this. I had an elderly neighbor would would flirt and come on to any man she saw. Yet apparently she treated her own husband appallingly.

If it were my mother I would have to say something. Its inappropriate and creepy.

A change in personality and inhibition could be a sign of a type of dementia that does typically have an early onset.
If she's always been like this - then it's likely just her personality.

If it's just 'her', what a horrible thing for you and your sisters and brother in law, I would be staying away from her unless she could act appropriately!! Completing with her daughters for sexual attention is grim, she should seek her sexual thrills elsewhere!!!

Presumable she’s very horny. As her daughters, get together and tell her that her thirst is showing, and to get herself a FWB or two.

From what you've said, and her behaviour in the past it sounds very much like histrionic personality disorder:

Craving attention/validation from others (especially sexual)
Cant stand not being centre of attention and will lie/exaggerate to be it
Dramatic behaviour- seductive and impulsive
Obsessive focus on appearance
Shallow, quick shifting emotions which seem superficial
excessive sensitivity to criticism

The fact she's coming on to her daughter's husband is particularly odd behaviour and is definitely not within the realms of "normal".
etc..