One way of gauging entertainers' popularity is to count how many times members are included in Twitter profiles. If you put someone in your profile, you probably really like them.
These Keyaki numbers are generated every month or so by a poster on 5channel, who counts only Japanese Twitter.
The top names by far remain Nagahama Neru, Hirate Yurina and Watanabe Risa. But when we look at the increase from late October's count to this count on the last day of 2018, we see good news for Hiragana, too. Risa is the top gainer, but the new Hiragana centre Kosaka Nao has gained more mentions than Neru (!), second only to Risa. And the members who stand beside her now, Kakizaki Memi and Watanabe Miho, are both in the top seven gainers.
The other big gainer I see is Suzumoto Miyu, who gained the sixth-most of any member.
Here are the full lists: first by absolute numbers, then by gains over the two months.
Mentions in Twitter profiles
[★=Gana 1gen ☆=Gana 2gen]
※()in brackets=increase 10/26 to year-end
14,452 Nagahama Neru (+315)
13,749 Hirate Yurina (+284)
12,036 Watanabe Risa (+398)
*7,745 Sugai Yuuka (+196)
*7,424 Watanabe Rika (+177)
*7,114 Kobayashi Yui (+149)
*4,751 Koike Minami (+157)
*3,877 Suzumoto Miyu (+268)
*3,540 Moriya Akane (+49)
*3,418★Saitou Kyouko (+176)
*3,149 Uemura Rina (+57)