Friend possibly splitting with partner - what does she need to know?

[Janus]

My very best friend is possibly splitting with her long term partner and father to her 3 children. I believe she has been subjected to mental abuse for years and his short temper has impacted on the family and she's contemplating asking him to leave.
I want to try and help - what does she need to know/do? He's the breadwinner in the house so I expect financial worries are the thing that needs to be considered first. They own their house but can he be made to pay the mortgage? Would she get any financial help elsewhere? I don't know where to start but any advice I could give her would be so much help.
Thank you.

[Me2017]

You say partner not spouse. This is an absolutely fundamental issue as the rights are utterly different depending on which it is.

Assumnig they are not married and the hosue is in joint names and 50% each (big assumptions), f there is abuse she may need to leave urgentl. If not better to stay put and reach agreement with him on dividing the assets or selling the house and splitting the proceeds.

if they are not married and the house is 50% each she may be able to stay in the house if she makes a Children Act claims (English law) and he may have to pay the children about 25% fo his after tax income but she will have no spousal maintenance as she is not a spouse. She should pay a solicitor ideally for a bit of advice.

She should also get all the documents she needs before they split and fall out such his P60s, tax returns, property documents, marriage certs, pensions details etc.