What action should be taken where one of two tenants has effectively left (deserted) the property

Other

I let a house near 3 years ago to a young couple with 2 children. They are no longer partners; the girl has remained in the house with the children and is now in receipt of Universal Benefit including the rental element. She is not working but undertaking a degree course mainly from home with a view to employment in summer 2023. We have a good tenancy relationship, and whilst there have been no missed rent payments she has said to me that she is struggling and receives no help from her estranged partner who has returned to his parents - and whose address I have. The young lady has been offered much advice as to redress options available to her - but seems independent. However, I envisage that arrears will shortly occur.
My question is that I would welcome advice as to how best I should plan for this event, and whether it is prudent to make contact with her partner (now removed from the house); and remind him that he is severally liable for rent and other matters of care?
What precautions should be put in place to void sliding into oblivion!?