Maintenance of funds

I ran into some problems with my tier 2 extension in regards to applying on time, I am now in the 14day with good reason time and the maintenance of funds requirements seem to have gone from having a set amount in your bank account right now to having over that for the past 90 days. This puts me in a pickle as I send money home every month to help support my parents and as I wasn't expecting to need to prove that I haven't maintained that amount. My friend has added me to her savings account (turning it into a joint) but that seems to be taking longer then anticipated and I'm getting worried. Is there anything else I can submit to prove I'll be alright for the next month (a letter from my friend confirming she'll support me financially if needed?) There is almost 10,000 in the account if that makes a difference.

Thank you for your help, anything people know will be greatly appreciated.

What is the 'good reason' you did not apply for an extension before your visa expired??

Note, lack of maintenance funds is not considered a 'good reason'. The maintenance funds requirements has ALWAYS been '90 days'.

What are the dates of your CoS?

My understanding is that maintenance funds are required for an extension but wait for others to confirm.