"I am going to the restroom."
It showed up earlier but then disappeared for whatever reason. Duo giveth and Duo taketh away it seems, I'm still waiting for 犬 to come back lol
へ puts an emphasis on the movement itself, while に puts an emphasis on the destination (and the objective of the movement).
おてあらいに行きます means you're going to the restroom to use it. おてあらいへ行きます simply means you're going to walk to the restroom, but you're not stating that you're going to use it.
It's more that it's a bit odd in English really. "I'm going to the bathroom" can be a future tense sentence (ie, I plan to go to the bathroom) whereas 行っています would require that you are currently in motion to the bathroom.