Communication is absolutely the bedrock of any relationship, whether it be romantic, platonic, business or any other sort of configuration. Indeed, one could make the argument that communication is the relationship, that two entities effectively have no relation to each other if communication - even if only the wordless presentation of one's existence - is not there.
I do feel that otherwise platonic relationships can survive one party being sexually attracted to the other and not acting on it. Heck, I feel that relationships can survive one party desiring to eat the other and not acting on it. Certainly, Ellen is already in a platonic relationship in which unreciprocated sexual attraction is present, but clearly things are different for her when that attraction runs the other way.
(Friday afternoon, EXT: car)
NP: So what are you going to do?
EB: What do you mean, what am I going to do? I'm not doing anything.
EB: I said from the start that a relationship with Jamie was a bad idea and I still believe that. We're fantastic as roommates and friends, we'd suck ass as lovers, and there's no way we could do friends with benefits. I can keep my shit buttoned down, and I'll eventually get over it.
NP: You have to at least figure out if he feels something similar towards you.
EB: I don't, actually. I don't have to do that. That is a thing that I do not actually have to do.
NP: Communication, though.
EB: Nope. And you're not talking to him either.
(INT: entering NP and JP's townhouse)
NP: Oh, I'm not going to talk to him. I'm not the one that needs to talk to him. But trust me, Ellen, this is an actual successful relationship talking. Communication is important. Communication is everything. More communication is always a good thing.
NP: JOHN, I'M HOME!
JP (offpanel): JOHN IS MY CLOTHED NAME!
EB: Yeah, okay, I think I'm gonna go.