Let's say we have one electron and put it in a magnet field. We find out what it's spin was along one axis based on whether a photon is emitted. But now we know with 100% certainty that the electron is now spin up along that axis. That is, if we turn the mag field off and back on without reorienting the field, no photon will be emitted.

Now lets say we have a pair of entangled electrons, meaning their spins are completely opposite along all axis'. Now we separate them. If we put one electron in a magnetic field, and it gives off a photon, then we know we have changed it's state. We know that before the magnetic field was applied, the electron was spin down, and the other electron was spin up along that same axis. But here's my question:

After the measurement, have both electrons flipped over, or just the one we measurered? Did the act of measurement screw up the entanglement?