Having the money up front mitigates most of the risk. The main lingering piece would be if, as a cosigner, you are on the hook for damages in excess of the deposit (on all leases I've used/seen a cosigner shares full obligation for all amounts owed).
So if she trashed the place or ran a meth lab, you could be on the hook for damages/remediation in excess of the deposit.
Another risk would be a reversed deposit of the funds after you signed. Many scams are structured around sending someone money and having that person turn around and send some gift cards or other non-reversible payment. Then the initial deposit gets reversed. That seems incredibly unlikely in this context.
Feels pretty low-risk to me on your end, she's taking some risk as well (you could run off with her money, though it'd hurt your credit score and you could face legal action, etc.).