Military Fiancé feeling annoyed

Yesterday having a conversation with my fiancé, she told me she has been feeling annoyed lately for no particular reason. Also feels depressed and trapped which I understand. She said that I don’t annoy her and it’s just a feeling that comes out of no where. Idk where this feeling came from all of a sudden. Her monthly cycle is coming around in two days and she said that might need the cause of her being that way or emotional. It was also mentioned that the vibe was off. We’ve been doing the samething before and after deployment. Calling, texting and communicating well and all of a sudden this wave of comments came. If anyone has any advice on how to deal with this it would be greatly appreciated. Feel free to private message or direct post reply