Housing Costs and leasehold service charges

Morning all
I have a client who has recently moved to a new extra care shared ownership property which she has purchased a 25% share in and pays rent for the rest.
She cannot own more than 75% of the property but if she stairways up to the maximum 75% there is no rent liability for the 25% remainder.
She cannot claim HB/CTR because her capital exceeds £16k at the moment.
She is receiving Pension Credit savings credit.
She has been told that the maintenance and service charges payable as a condition of her occupying the accommodation as her home are HB items and cannot be included in the Pension Credit assessment as a Housing Cost.
If Housing Costs were added into the assessment they may well tip her into guarantee credit and she could therefore claim HB etc. via passporting.
It seems to me that she is being discriminated against because she only owns 25% and is treated as a shared owner when someone owning the maximum 75% could get the Housing Costs included in the assessment of Pension Credit.
I’m going around in circles trying to understand this so can anyone help me with specifics about the regs and when Service/maintenance charges may and may not be included in means tested benefits as a Housing Cost please?
Many thanks
Lynne Davey