So it is improper to say that women cannot enter the altar.
But rather, that nobody who isn't there for an approved purpose can enter the altar.
There are always exceptions. I suppose that if we needed something like the sink in the sacristy repaired or the wall painted and one of the workers was woman, she could enter Altar.
Fr. John W. Morris
... and the apse in the altar of the church I attend was painted by a female (layman, not monastic) iconographer, with the blessing of her bishop, because of her particular skill in painting on curved surfaces. The other iconographers who painted this church were an abbot and one of his monks.
However, she only did her work when a service was not in progress. She was not serving in the altar as altarboys do.