Bank balance exceeded the legal amount

I am a carer to someone of 33 years and she is claiming E.S.A and P.I.P for her disability. All her benefits (Including mine) are paid into HER bank account. My benefits are carers allowance and Income Support. Back in 2017 I was left an inheritance by a great uncle so I decided to put the inheritance in the SAME account. The other day totally out of the blue I had a phone call from someone from E.S.A asking how much was in her account....Totally shocked by this I thought it may be a hoax call so I didn't tell them anything...they said they would write to me asking for evidence of her bank account details. They stated that anyone is only allowed so much in their bank account before their benefits would be effected. Having researched this I have since discovered that £6000 is the limit of savings before benefits are effected. The funds were triple that amount due to my inheritance. The E.S.A also stated that if the inheritance was ONLY in my account as I am on care allowance - it wouldn't have effected anything. Luckily I have a recent bank statement and also a solicitors letter stating the amount of my inheritance of which has now been transferred to my account. The person who's account has since transferred my inheritance to my bank account of which leaves her account less than £2000 of which is way under the £6000 limit. The E.S.A have requested bank statements from 5 years ago which is impossible to obtain. I am hoping that the letter from the solicitors will verify as to why the funds were so high. I am hoping the proof will verify all of this and it was a genuine mishap on my part by having the inheritance paid into her account. Any advice greatly appreciated.