Loan application and terms I did not agree to

I need some help for my aunty, who has recently been duped into a 10 year loan with tesco bank by a solar panel company.
This is really long so sorry for lengthy read.

My aunty had solar panels installed on her property which stopped working she contacted the insurance provider who said they didnt cover the repairs as they notified them too late.
Anyhow, so this guy came round advising he worked with tescos, a company called go green and that they could sort out the problem my aunty had with her solar panels and also advised about battery storage (which is what they sell)
Now as he said he worked with tescos my aunty trusted him and thought there isnt a risk of the company ceasing to exist like her solar panel company, and she had security as tescos was a well known reliable company.

So these guys came round to her house explained to her about the system they would install how it would help, and that they will buy her out of her old credit agreement and then she can continue to pay GoGreen. They also mentioned that she would be paying £140 a month and this will cover both the payment to the other company and also go green. She was already paying £120 for the solar panels and he persuaded her that she would be paying £20 more and will have a working system and save money, as at the moment she is paying 120 for a system that doesn't work. She said they said they were going to see whether they would be accepted and started typing stuff away on their tablet asking their name details and nqormal form type questions (like the old company did) so she assumed they were credit checking whether she would be successful) turns out she was...
And they got her to sign a. Yellow invoice saying that they would take this battery system from them and get the solar panels fixed for £7950, the guy then said you will receive a payment and you will call up and pay the old company, and then the remaining amount will be paid to Gogreen, she didnt question the buy out as there is no link between gogreen and her previous financer, she realised she would need to make the payment.

A few days later she received a text from tesco saying her loan was approved, and paperwork would follow. The work got carried out quite quickly pushed by gogreen, and shortly after her father got took very ill that she forgot about the paperwork coming from tescos, which never arrived.
Her husband then realised he was constantly putting money in to the account l, he got his daughter to check the bank and print off a bank statement (as neither are tech savvy, hate setting up direct debits etc) . Turned out they were paying tesco £226. She was really shocked and upset because they cant afford this much they had agreed to 140.
After a few phone calls to tesco, CAB, etc tesco advised that they had digitally signed the terms and conditions online and no paperwork would come out to them except a welcome letter, which she did receive.
Turns out those guys had applied for a personal loan with tesco, digitally signed the terms and conditions, so all payment amounts etc would have been stated at the time on the digital screen (the guys never showed her or her husband the tablet) and now its turna out they took out a £12850 loan, with an 18.9%APR over a 10 year period they will pay back over £27000. Shes absolutely distraught and upset and now doesn't know what to do??

I contacted tesco fraud for her who have advised it's not fraud as they were there. Ombudsman said it's not tescos fault. I have written a letter to go green, but when we rang them, they denied their affiliation with tesco and said that they recommend tesco loans. Shes really upset and its affecting her health, she is already struggling financially. Any help would be appreciated guys thanks