With their nice downtown breakfast done, Nancy needs to get back to her real job. Since the restaurant is just two blocks from her office and it would take the same amount of time for her to get to Paul’s car in the garage, she doesn’t have any problem walking.
This just leaves the problem she’s still wearing the same clothes she wore yesterday.

As she says in the strip above, She has a change of clothes in her office which is proper. Of course, this leads to the question of why doesn’t she have a change of clothes at Paul’s, considering how often she stays there.

Nancy doesn’t like people thinking she’s dependent on them.

Yes, we’re all aware there are several flaws in this argument, and if you want to point them out to her, be my guest.

Besides, who’s going to notice her changing in the bathroom, right?

I don’t expect anybody to remember Stella. She’s one of those characters I expected to be a semi-regular who promptly disappeared.
Anyway, she’s Nancy’s primary office rival who frequently trades quips and barbs with her. This is her first appearance in 16 years.

Of course, she’d notice Nancy’s wearing the same outfit she wore yesterday.