Definition: To come or go into (a place).
Gloss: /\ROOM/\ IX2 /\ENTER/\, IX1 LOOK-UP.
English equivalent: Mary looked up as he entered the room.
In the first clause, this clause is an OSV (object-subject-verb) structure. Raise eyebrows (/\) for the object ROOM.
IX2 is a pronoun (referring to 'he' in this English sentence), whereas IX1 (in a different referential space) refers to 'she'. It doesn't matter which space point you want to use as long as you constantly refers to the same referent throughout a sentence(s).
Raise eyerbrows toward signing ENTER, which indicates a 'when' clause.
In the second clause, the verb LOOK-UP is inflected to agree with the subject-object.