pensioner JT. , DHP or HB

My customer is in UC and has applied for a DHP to cover the dhortfall in his rent.

Customer moved into property 202 when it was him and wife on teancy
When tency renewed June 2022, MIL was added as anamed tenanct
Appears UC dont know about this as still basing on 1 bed LHA and full rent, rather than 50% of rent. ( This will create approc £600 pcm o/p if/when UC find out)

CIS Info .
Customer is bangladeshi, in UK since March 2012.
Wife is listed as Italian in UK since at least Jan 2016
MIL in UK since March 2022, listed as Bangladeshi

we dont have passports/ HO visa/ EE status for anyone.

MIL - Can we pay HB?
CIS shows not entitled to state pension, but no indication she has applied for pension Credirt.
If she is here as a familiy member of the Italian daughter, would dshe be lweligible for HB?
Im thinking that while MIL may have PRE SETTLES status, she would acquire the same R2R as her daughter.
Her daughter has been in UK since at leat Jan 2016m, so potentially would have a perm R2R by Jam 2021 - so would MIL get that rtoo?

Not clear if italian wife has ever exercised treaty rights , no record of any earnings etc.
Husband has worked so if he has EEA passport, he would have perm R2R, which his spouse would acquire automatically.
If wife hasnt worked, would she get a perm right to reside for 5 years residency? in HB we’d want her to be exercising treaty rights ( working, retained worker status etc) but not sure if that is essential.

I dont want to do a DHP for UC claimant if I can pay HB to the MIL
Would MIL be eligible for PCGC if she is family member of EEA national with a perm right to reside??

I think my starting point is rto see passports/visas/Hon office info re everyones right to reside status so I know which set of rules we need to apply ?

Any pointers/advice most welcome
Cheers!
Confused of Kirkoswald