1) Regarding Arwen raising the fords of Isen, not true. It is Elrond who does that, Arwen does not make an appearance yet.
2) Regarding Glorfindel, he is not on the same level as Elrond. Glorfindel is a "simple" warrior and he plays the same role to Elrond as he did to Lord Turgon. Advisor and Military Shock Factor Trump Card. Everyone embedded in the darkness shits themselves when they see Glorfindel in all his light.
Regarding Arwen, she does not play a "minor" role in the books. She does not make a direct appearance much, but her existence and character is crucial to the plotline and she constantly appears in reference or in background passing without a direct link. Put it this way, without Arwen's existence the "good" side loses the war and Sauron becomes victorious. Why? Because Aragorn wouldn't have showed up.
On the top layer, we are introduced to Aragorn as this confident, brash hero who is desperate to become King and will tell anyone and anything that he is the rightful heir of Elendil and Isildur. But why does he want to become king so bad? Well, 40 years prior to ROTK, Aragorn already had the perfect opportunity to become King. He had the command of the entire court, Ecthelion favoured Aragorn over his own son, Denethor and Aragorn could easily have taken the throne then and there. Instead, he goes wandering around Harad, goes to Mordor and then heads back to Lothlorien before going to the North and residing with the Dunedain for the next 35 years. Why?
Well, the answer to the question, to put it in modern terms, is that Aragorn was a ****. Edit For some reason S1MP is filtered out.
In the first half of his life, he meets Arwen and Elrond tells him that she isn't good enough for him and that he must do something great to ever catch her attention and that he is too young. He basically sets out immediately and does "great deeds" to prove himself.
By the time he enters Lothlorien, Aragorn is "weary" of the world, and lost most of his motivation. He doesn't really have cares for the chaos of the East and he sees much suffering and destruction. He doesn't have a desire for power despite basically being the most popular man in Gondor as Thorongil. All he wants to do is go home to Imladris and live a simple life before going back to the nomadic ways of his people.
But in Lothlorien he meets Arwen again, who loves him back after 29 years apart and they become engaged. Aragorn goes back to Imaldris to ask Elrond for her hand, having "proven himself to her." But Elrond says this:
Basically, Aragorn had lost motivation, but Elrond dangled his daughter's hand in marriage as a carrot for Aragorn to become king. Without this motivation, Aragorn would have long lived his life like the previous Chieftans of the Dunedain or married Arwen and lived out his life in Imladris. Essentially, Aragorn's entire motivation after 2980 T.A was to become king so he would marry Arwen.
This is alluded to multiple times in the books, with references that are hard to understand:
When the Gray Company arrives and Halbrand passes Arwen's message, it is this:
It's not "Your hope of being king", its, "Our hope of being together."
It is Arwen's banner that turns the tide of Minas Tirith. When Halbarand raises the banner into the air, the Gondorians and Rohirrim's morale is raised immediately because their reaction was, "Holy fecking shit, Elendil has returned YESSS!!!!"
Orcs reaction was, "What??? But how can this be? His line ended 800 years ago!!"
For example, when Eowyn begs to go with Aragorn to go with him and Aragorn rejects her, she complains that why is Aragorn allowed to do what his heart desired but Eowyn was not. Aragorn replied that his hearts desire was not to fight this war but to be with Arwen:
When the war is finally over, but after a few months Aragorn falls into despair because he does not know what happened to Arwen. He literally laments that everything he did was for nothing and that what use is there in being king if she is not here. Only when he discovers the seed of Nimloth does he feel hope again:
Note that his implication here is, "If Arwen does not arrive, the line of kings will fall because I will not have children or marry anyone else; nobody else will be queen."
There are plenty of other references signalling the importance of Arwen, such as Aragorn naming his horse Roheryn.
Tl;dr Half of Lord of the Rings is one guys quest to get laid, becoming King was basically just part of the process of achieving his ultimate quest.
So to reduce Arwen's role as "minor" and "eye candy" just because she doesn't appear directly in the texts is wrong; without Arwen, Sauron ultimately wins.