Is this weird?

Me and my partner both announced on Facebook last night that we were expecting out first child together, this morning I wake up to find that his ex has commented on the post saying 'congratulations x ', him and his ex don't get along at all after she had an affair for 2yrs behind his back. She has constantly tried to split us up on numerous occasions by saying my partner wants her back and he's slept with her on such a day ect none of it is true, we don't live in the same area as her. Why would she be commenting on such a personal post of ours?