yeah, AE-LOCK with the centre AF point and then re-compose.. spot metering mode.
other options: take metering with the centre AF point over the subject's face or wedding dress if that was important, then switch to M mode and use ISO, T and F values.
alternatively, continue shooting in the Evaluative mode but use exposure compensation:
in AV mode, take a spot metering with AF on the subject's face and then another one in evaluative mode. take note of the shutter speed values.
evaluative mode shutter speed could be up to 2 full stop slower. use the number you have found to set the exposure compensation correctly.
and the straight forward option: use a light meter..