calculating ESA backdate for single person with period of joint JSA claim

Hopefully just a quick one.

Single client on IR ESA, failed LCW assessment had nil income for a while then got back together with her ex and made joint claim for JSA for about 2 months before separating from him again and eventually going back on ESA as a single claimant pending appeal. Has now won the appeal and will get approx 15 month backdate of SG component,  EDP and some periods of missing personal allowance.

I’m trying to work out what backdate she will get but am not sure how the period of her receiving JSA at the couples rate should be treated in the calculation. She was the lead claimant with her partner added. Do I count her income received as her personal allowance of £73.10, or half of the couples entitlement of £114.85 =£57.43?

And would this be different if her partner had been the lead claimant instead of her?

Thanks