I don't usually try to ID clothes, because I'm not well versed in that area. But even I can tell a Diane von Furstenberg dress when I see one, or in this case, like a dozen.
God bless you Pam. Here are all your DVF dresses in episode one:
AKA Ladies Night:
When we first see Pammy, she's at the reception desk, showing an impressive amount of clev. Get it, Pam. The dress is a Tallulah diamond wrap pattern, with red cuffs and hem. Very pretty.
When next we see Pam, she's romancing Jeri Hogarth, her boss--and clearly the two ladies have an established, intimate relationship.
Pam's dress has a dark background, with a very pretty floral pattern all over--and a square/geometric pattern around the v-neck. The dress is the Tallulah floral pattern with geometric trim:
Pam's last DVF dress in episode 1 is a black and pink geometric print. It's also the dress that we, the viewers, see Pam realize that Jeri's not quite as free as she may have lead Pam to believe. Pam witnesses Jeri kissing her wife and it seems pretty clear to me that Jeri has yet to break the news that she wants a divorce. Pam realizes this as well, quickly going from a delighted smile, to a shocked stare, then awkward exit. Ouch, Pam. But so much worse is yet to come for you.
The dress is clearly the Zoe, pink geometric pattern, but I can't find a version online anywhere with the v-neck that Pam's sporting. Makes me wonder if the dress was altered for Susie's character? Most of Pam's dresses have a plunging neckline--and I'm thinking the costumer gave this one a similar treatment? Super cute dress either way. Up close the pattern's really lovely.