Student or Learner
Wallflower seems to mean "unpopular person without any dancing partner", so does it mean only that kind of person or someone who doesn't talk much being silent? What other similar expression do you have?
ex)A:Look who's here! I'm so happy to see you here, Bill
B:Good to see you, too. Let's go out on the dance floor.
A:That would be great. I was just sitting like a wallflower until you came.
A 'wallflower' is a rather insulting way to refer to someone who is shy, withdrawn, and uninteresting. 'Wallflowers' do not dance. They also do not make good conversation partners. They are not fun to have at a party. They do not go out of their way to chat. They are not fun to have around. They may be very nice and good people at heart, but they have no social skills. Wallflowers are not bad people, they are just dull.