Confirmed what ? She still don't know what her love is. Don't start confirming anything on your own. Youall know that Japanese and their notion of saying "I love you" is tricky so it isn't because the translator put "I love you"that she suddendly love them romantically. For one it's too sudden that after seeing one poly couple, she think "oh man i'm gonna poly with my roommate", that make so little sense. I mean, it's great that the adults poly is working but that doesn't mean it's gonna work for thr girlsfor one and two, that doesn't mean all the girls became ok with Poly just because MC said she love both of them.. The adults just told her to find her own way to express her love, they didn't say "do the same as us".
I mean it did also establish, Rina isnt exactly someone who does the whole, only one partner, since multiple arrows, as you said.
Do we know if they're really arrow of real love and she is just searching for affection for anyone who is niceto her. Also yea, about the little arrow toward the friend, see how she is gone after MC say she love them. If MC saying anything nice to her is enough to break any little arrows, that mean she never really had any real feelings for thos her littles arrows pointed to.