Both Yuka and Shikamaru possessed low-key personalities. The former only appeared somewhat high-profile due to her status, though she wasn't actually fond of drawing attention, while the latter utterly despised standing out and thus constantly tried to minimize his presence.
Even after becoming a couple, the two did not make a big show of it.
First, Yuka dared not publicize it. She was terrified that Sasuke, who was off God-knows-where, would hear the news and come rushing back at breakneck speed to drag Shikamaru off—in Yuka's mind, Uchiha Itachi was already aware of the situation (really?) and definitely wouldn't have any objections; only Sasuke would object! (This was a severe bias and misunderstanding regarding Sasuke!)
Chapter 279