Personally, I just see it as the creator's way of drawing it out as long as possible, Emily holding off inserting an actual dick in either of her bottom two holes.

She's already inserting it in her top hole (mouth) and with her doing so, there shouldn't be any reason to delay anal at this point as well.

Now, if she hadn't done oral at this point, I could see what you're bringing up here as a valid point but she's already shown though that even if she's apprehensive about sex, as reserved as she is, she has an aversion for it all the same.