Let's take a look at the symbolic final images Miller gives us at end of the first two scenes. Scene one: Catherine lights Eddie's cigar. Scene two: Catherine pours sugar into Rodolpho's coffee. Random? We think not.
The first one seems pretty obvious. Cigars are time honored phallic images, meaning they bear a striking resemblance to the male genitalia. Catherine sets Eddie's "cigar" on fire. Need we say more?
Then Rodolpho shows up, and we end the next scene with Catherine pouring her sugar into his cup. The sexual connotations aren't quite as blatant as with the cigar, but we think they're still present. In any case, it's important to note that, in the pre-Rodolpho world, Catherine attended to Eddie, but now her services are starting to go to the Eddie's virile young challenger.