Yes, REPLIES is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, P 3, L 1, I 1, E 1, S 1.

Is it a valid word?

REPLIES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a statement (either spoken or written) that is made to reply to a question or request or criticism or accusation
the speech act of continuing a conversational exchange