The affix yat comes in the sense of 'what bears it' after the word janī being in Accusative -2nd case construction, the whole word being a Name.,
Thus जनीं वहति = जन्यः 'a friend of a bridegroom,' fem. जन्याः 'a bridesmaid.' The word जनी means 'bride.' जन्या lit. means 'what bears the bride' i. e. who carries the coy bride to the bride-groom at the time of play &c.,