The charge on her property means that when she tries to sell her house she won't be able to offer clear title deeds to the new owner until the debt to the charge holder (you) has been redeemed.
Who ever buys her house will be advised by their solicitors that they cannot complete the purchase until the title is clear, so if she wants to get paid for her property, she will have pay you. Once you have been paid, her solicitor will apply to the land registry ( who the charge is registered with) to have the charge removed from the title deeds, and she can then offer clear title on her sale.