Essentially the answer is: yes. There's no way to use a referral link for an account that has already been created. She will need to start over with a brand new account and start from scratch if you want to leverage the referral
This.
And it will need to be on a device that doesn't currently have Raid installed. Just as an additional FYI.
Here's my install link for Raid: Shadow Legends. Get it through this link and both of us will get some free stuff to boost us along! https://link.plrm.zone/app/ejmce