Hello sweet_cookie08,
When we applied for my daughter's settlement visa, we have submitted photocopies of yahoo chats, emails, remittance slips, my payslips, my tenancy agreement in the UK, bank statements, etc - all these you can find on the UKBA website (check the guidance on settlement visa). However, she was refused because of the "sole responsibility" reasons and also because I have been separated from her father without any annulment or nullity of marriage that was why the ECO stated there is no evidence that proves that. Your case is far much different from me as you will be joined by your husband. You just need to gather evidences that though you have left your daughter in your mother's care, you must show that you are still in charge in taking the important decisions in all areas of your daughter's life e.g. schooling, finances, health and you must establish that you are always in contact with her e.g. chats, emails, birthday cards, photos etc.
I am not really knowledgeable on this area but through experience, as I am now going to my court hearing, I can only advise you as far as I know. Research more on the topic of sole responsibility on the internet and I am sure you will gather more info.
I hope I extended a little bit of help. Good luck!
