Eva Stratt didn't send Grace into space to die.
The death of the astronauts was never the point. They will all die, and most more horribly than whatever method the Hail Mary crew can choose in space eventually. But they were send on a mission.
She sends Grace because she has full faith that he can do something deeply meaningful there with the time he is given.
She is not sacrificing his life. She is sacrificing his choice to refuse. Because she loves the entirety of their planet more than his ability to choose where to die.
But, at least in the movie, it is act of faith in him that is absolutely immense. It is also an act of love.
She knows that he will find his feet, that he will put himself to work, that he will make his best effort to find answers, in whatever way his unique and agile brain can. And that he will find meaning it that, too. Because he is a fundamentally good and brave person, underneath the constant, deflecting, terrified insecurity.
There is no universe where he could have lived in peace, free of crippling (justified) shame, had he gotten his way and stayed. Not with a quantifiable cost of human lives attached, running in the billions, just from the delay alone. His life was over the moment of the explosion. The choice to go existed and it was always going to be the full realization of Ryland Grace as a person, or his obliteration. The way he draws up his glasses, pulls on his hat, retreating into an empty shell, "I don't have it in me", that was a kind of death, too.
"This may seem like me betraying you, but it's actually me believing in you."
"You'll do great, you know who you are."
When Grace buries Yao and Ilyukhina, the most meaningful thing he can find to say about these strangers is "You were very loved". And they were. It's why they went.
But so was he. In so far as faith in the best parts of a person, the refusal to let them be destroyed, can be a variant of love.