From what i have gathered, the lag and desync being experienced is because my gf and I are using the same network. Since mistlands. Whoever logs into the server first seems to hold some kind of priority, as that person wont experience any lag/desync. Ive tried this with both of us taking a turn to log in before the other. And it played out as such.

If we put distance between us (because only today did we try going to a new island together) that is when the lag will disappear. But the closer we get, that is when one of us starts to experience problems.

Ive only tried to test this with me being on a different network. Attempted to use my cell phone as a hotspot, but that was also lagging I think only because the data rates were pretty low apparently.