Well, we don't necessarily know it's God (with a big g) it's implied to be God, however. Though, the interesting part of the scene is not the depiction of God in my opinion, but rather, the character doesn't recognize Klaus and it's indifference to him. Regardless, I digress,
This answer depends entirely on how much you want to take from the comics or not.
The show is actually cobbled together over several different comics and mini series, The character is explained in the following youtube link, at this link And directly shows your scene in the comic books.
It is nothing more than God, who is a cowboy on a horse telling Klaus that he is basically neither welcome in Heaven nor hell, and he's going back because of it.
It's not nearly as interesting as in the show (I infact, find the show considerably better than the comics.)
So there is an obvious, and interesting change from the creators of the show. Of course, a rough old cowboy man, to a small young "innocent" girl on a bike with flowers.
At worst It's a boring gender swap.
At best a deliberate change, trying to show, just like all of the characters, and Vanya at most, nothing is what it seems, one shouldn't expect anything.
In the middle, it's a boring attempt at 'changing expectations' Which is popular in film nowadays.