The word 'apostle' appears quite a lot in the NT. primarily it is applied to the Twelve whom Jesus chose to accompany Him in His public life. However, others are referred to as apostles, from the Greek, 'one sent out or away' which could be applied to anyone sent out to spread the good news, the 70, for example.
The washing of the feet was a ritual which took place when guests entered a household in those times and of course it has its symbolism for us today.
The Last Supper, however, was particularly concerned with the Eucharistic Sacrifice where Christ, the High Priest sacramentally prefigured His bloody Sacrifice on the night before He died and decreed or 'ordained' that the twelve continue with this unbloody sacrifice until He will come again. This was the first Mass.
There is no mention in the Scriptures or in Tradition of there being anyone at the Supper apart from the Twelve so your belief that there were others there including females is pure speculation.