Explanation: all the staff of the restaurant in this anime seems to be introduced, but once in a while, that unintroduced waitress appear without explanation, and at this point I wonder if this will change in a later episode or remain a mystery/mistake.
Aw gawd. Fried noodle sandwich is a real thing, not something invented for Azumanga Daioh. (The characters call it 'fried noodle subs' in the English-dubbed anime)