Made a mistake

Applying for uni loans for 23/24, inc. higher maintenance loan. I put that I wasn't in contact with either parent however now have contact with my mum, and want to be assessed on her financial info.
1) Does she fill out a pff2 form or can she just make an online account to link to mine?
2) If I upload a pff2 form is it okay for her to give an electronic signature?
3) As this isn't technically 'asked for' evidence, will uploading it mess with my application?
4) Do I need to include a cover letter? Is this uploaded separately or included in the form somehow? What would I need to say?