Grace and Peace to all,
‘All’ Catholics, male and female, are admitted to the Most Holy Sacrament because without it no Catholic would fulfill the divine command of Our Lord and Saviour to ‘eat of his flesh and drink of his blood to everlasting life’.
Our Lord promised the Jews at Caphernaum that He would give them His flesh to eat and His blood to drink (John vi.).
After the miraculous multiplication of the loaves and fishes the people went in search of Christ, and found Him in the synagogue at Capharnaum. They wanted HIm to give them bread again; but He promised to give them the bread of immortality. When they asked Him for it, He answered: “The bread that I will give is My flesh.” And when they refused to believe His words, he added: “Except you eat the flesh of the Son of man, and drink His blood, you shall not hath everlasting life, and I will raise him up at the Last Day. For My flesh is meat indeed, and My blood is drink indeed” (John vi.52-56).
Your first error is to ‘limit’ your argument on the texts of the Sacred Text alone and not include the consensus of the early Church. Your second error is in ‘equating’ the Apostles present at the Last Supper as an indication that only men may be leaders in the Church and only men may have Everlasting Life… we know quite well through Mary Ever-Virgin that such is not so as she was admitted to heaven and so Crowned. Glory to God!
So to answer your question “Why are women allowed to receive Communion” we must say because God has extended to ‘all mankind’ (i.e. male and female) the gift of Everlasting Life.