So many things... we will need a video or atleast a shred of detail.
My wife said it's prob a female trying to lay eggs
Is it a swordtail fish since you said 'sword'? I haven't kept them, but I think the males have the sword. Not sure about their mating dance ritual.
It is a gonopodium, a modified anal fin, that the male livebearer uses to deposit packets of sperm into the genitalium of the female. A livebearer fish version of a penis, yes.
Awww... he was just lonely, lol