I suppose that depends on your definition of "romanceable." If you mean getting to go all the way with her, no. If you mean very limited physical and a bit of emotional interaction, then sure, you could say that.
The way I figured out how to code it without making a ton of work for myself is that you'll see the Mono route scenes on both routes, and the Poly route scenes are extra scenes interspersed between those here and there. So it's not a true branching path, 'cause then I gotta do 2 separate stories for the same character and I already have 48 more of those to do (since Senia is finished).