Does anyone know which episode Jeanne d'Arc is in (or where I can find the webcomic)?

Jeanne D-Arc, or better known as Joan of Arc has made two appearances in Hetalia; one in Axis Powers and another in the Beautiful World series. In the Axis Powers, Joan is seen in Episode 10 in France's reminiscing about how he used to be strong. In it, England (dressed as a knight) with his army is mocking France and calling him a "loser". Joan of Arc is seen in front of France, turning her head around so the viewer could see her face, and asks France, "What does he mean by 'loser'?"
In Beautiful World, episode 15, France tells a tourist (some people think the tourist is the reincarnated Joan of Arc) about the Hundred Years' War and about Joan of Arc. Her whole body isn't shown but she is seen kneeling to the Prince.
I hope I answered your question!

She isn't in the show, and she only has one panel in the comic. Here:
link

Shes in one episode for like 2 seconds I think it's in the 2 nd season where England calls France a looser and she asks France what is a looser, can't remember the exact episode though.

I can't remember the episode, but she's in it. See this is her in the anime.