The Halifax are very unlikely to go for a repossession on 3 months mortgage arrears. They are under a duty to contact the borrower and offer advice and make arrangements to pay the arrears back at an affordable rate and this is why a counsellor will be contacting your relative.(posted 7255 days ago)By all means help your relative as you can, but you are not party to the mortgage agreement and therefore cannot make any arrangement which would preclude Halifax from taking possession proceedings if the arrears reached the point at which they feel they have no alternative - that point varies with each circumstance and each lender.
If Halifax did take your relative to court, they would be extremely likely to end up with a suspended possession order with your relative being given time (as much as the remainder of the mortgage term under the "Norgan" rules if need be) to clear the arrears so long as the future monthly dues are met in addition. However, it is best to avoid letting it get this far if she can.
Your relative should write down her income and outgoings in readiness for the phone call and stick to what she can afford rather than allow herself to be bullied into an arrangement with Halifax that she cannot keep.