Apologies, I should have read the title of your topic more carefully 
In that case, she’ll need to contact the customer support team to follow up on this.
My guess is that perhaps you didn’t include the 9 digit reference number, when you sent the transfer? In which case, once your friend follows up on this, the team will be able to simply move the money to her account 
In the future, I’d recommend using Monzo.me to send her money, as those transfers are instant & can’t get lost. Or if you sign up to Monzo, you can send each other transfers instantly from within the app 