IPV4 & IPV6 Log In Issues

Ok so we have a client login area that only allows one person to be logged into the account and the older one gets kicked out. Basic stuff. We have a client who is showing both IPv4 and IPv6 in the logs. It is the same person but the system is thinking it is 2 because of the dual headers. Does anyone else have this problem? I am assuming the client got a dedicated IP and they assigned her both IPv4 and IPv6?

Did anyone find the fix? She keeps getting logged out of the account because of the dual headers.

I see the Pseudo IPv4 option but says it is suggested off.