She wasn't really right. The Alliance would never have been able to handle things on its own, and had to bet everything on their allies staying allies.
I'm also still a little bit confused as to why you're so adamant that she doesn't even have the tiniest amount of speciesism.
She was right because the Alliance's allies didn't stay allies. They abandoned humanity (and everyone else) to try and save themselves. Shepard had to jump through numerous hoops to convince them to stand together.
This is not to say there aren't problems out there which are simply too big to handle alone. But the crisis in ME3 proved Ash's point that when push came to shove, the turians would look to save the turians first, the asari will look to the asari, the krogan will look after the krogan first, etc.
It's simply a survival instinct. It may not be the correct instinct for the situation (as the reapers were more than capable of dealing with the galaxy piecemeal), but it's a natural response to save your own species and ensure it continues.
And what I am adamant about is that while Ash is firmly, perhaps even fanatically loyal to the Alliance, she is no more speciest than any other human. And less than some. For years I've been listening to people calling her a racist, a bigot, and worse because they were determined to think the worst of her.