All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
There is no harm for these women to pray in the manner described in the question. It is permissible for women to pray in congregation while the one leading them stands amongst them in the middle of the row. Um Waraqah Bint Nawfal from the Ansaar used to lead the women in her household and the Prophet appointed a person to call Athaan of the prayer for her. This is a sound narration reported by Ad-Daaraqutni, Ahmad, Al-Haakim and others. It is confirmed as well that 'Aa'ishah and Um Salamah led women in prayer, as reported by Ibn Abu Shaybah and others. It is also permissible, in general, for a woman who is praying in congregation with other women to correct the one who are leading them in prayer. Anas said: "We used to correct the recitation of the Imaams during the era of the Prophet ." This narration is of the same ruling as the saying of the Prophet . Indeed once the Prophet was confused while in his recitation when leading a prayer with the companions and after the prayer he asked Ubay Ibn Ka'b : "Did you pray with us?" So Ubay Ibn Ka'b replied: "Yes." Therefore the Prophet told him: ''Why did you not then correct me?"
Allaah knows best.