It would depend on the day, her mood. Maybe if were open for dinner, or threw nice soirées, but even then it would be a stretch. Fred in the books — or Paul in the movie — would do all he could to book her the reservation, but there's no telling she would show up. It would be too much of a reality, a dream she's not ready to fulfill.
Maybe in the movie she was less of an indecisive person, but in the book she was just a young girl trying to find herself. The book began when she was only 19 and followed her through her early 20s. She was somewhat of a high-end call girl, in contrast to the socialite figure Hepburn turned her into.
Most importantly, she went to Tiffany, not necessarily because she loved the jewelry or the diamonds or the silver, but because there was something about it which settled the angst inside of her; the anxiety of life.
"I don't want to own anything until I know I've found the place where me and things belong together," she said in the book. "I'm not quite sure where that is just yet. But I know what it's like... it's like Tiffany's."