Mrs. Wexler shows oblivious disdain for the other heirs as they enter the mansion for the reading of the will. Why do you think she is acting so snobby?
Mrs. Grace Windsor Wexler is rather a snobbish woman. She imagines herself an interior designer and thinks that she is the logical heir to Sam Westing's estate. She thinks that she will soon come into possession of Sam Westing's fortune because of family gossip about a rich uncle somewhere in the Wexler ancestral line.
This is why she shows obvious disdain for the other heirs as they enter the mansion for the reading of the will. They all look like servants or employees to her. Allowing for the apparent low status of the other heirs, she imagines that they are only there to receive the sort of recompense a generous employer would bestow on them upon his death.
She is especially contemptuous of Otis Amber, the delivery boy, who is in reality a rather skilled and discreet private investigator. Mrs. Wexler is just as dismissive of Judge Ford (who is black); she thinks that Judge Ford might be there in a legal capacity or that perhaps the judge's mother had worked for Sam Westing as a household maid. Mrs. Wexler knows that the Judge can't be related to Sam Westing; looking around at all the other heirs, she definitely thinks that she is safe from the prospect of any of them upstaging her as the heiress of Sam Westing's estate. In fact, that's exactly how she describes herself on the receipt that she signed. (The receipt was signed as proof of acceptance for the letter she received from E.J. Plum, the attorney. Letters were sent out to all the heirs of the Westing estate.) Alas, her dreams of being the sole heir are dashed when Sam Westing's will is read. The will states that there are sixteen heirs!