wicegrid to show title in many to many table

i'm using WiceGrid to build a table in users index with some filters, my table shows data from a table called users and a table called states. Those tables are connected by a table called users_states, so the relation between this 3 tables is this:

user: has_many :users_states

user columns: id name

user_states: belongs_to :user belongs_to :state

user_states columns: id user_id state_id

state: has_many :users_states

state columns: id title

my objective is to create a dropdown list filter in my users index table that contains the titles of the states that are populated in the index table. Something like this:

but what i have now is this:

users_controller.rb (index)

  def index
    @users = current_user.auth_users
    @users_grid = initialize_grid(@users, include:  [:states, :users_states], per_page: 20)
  end

index.html.erb (users)

<h1>Listing Users</h1>

<%= grid(@users_grid, show_filters: :when_filtered) do |g|

  g.column name: 'Photo' do |user|
    image_tag show_photo_user_path(user), width: '100', height: '100' if user.photo_filename
  end
  g.column name: 'Name', attribute: 'name' do |user|
    user.name
  end

  g.column name: 'State', attribute: 'state_id', assoc: :users_states, custom_filter: :auto do |user|
    user_state_last_title(user)
  end

  g.column do |user|
    link_to 'Show', user
  end

  g.column do |user|
      link_to('Edit', edit_user_path(user))
    end
  end

end -%>

user_helper.rb

  #method for aquiring last state from user
  def user_state_last(user)
      user.states.order('users_states.id').last if user && UsersState.where(user_id: user).last
  end
  def user_state_last_title(user)
    user_state_last(user).title  if user && UsersState.where(user_id: user).last
  end

can anyone help me please? thank you very much!