Oh OP I’m so sorry you’re hurt by this, and a bit bewildered by the sounds of it. But really it’s more about a communication gap than anything else. It’s completely natural that you’re assuming that she’s thinking and feeling what you would if you had said what she said. In fact it’s almost impossible as a neurotypical not to make those theory of mind assumptions, anymore than a fish could analyse water - these are the waters you live in.
But this is an example of your neurological processes not mapping. Love is kind of a foggy concept, amorphous, difficult to define, impossible to explain and yet you just know. But autistic brains don’t do foggy concepts. In all likelihood she is experiencing all, or most, of the constituent parts that you could break “loving” into but she doesn’t smush them together into a cloudy miasma. It doesn’t make it less - just different.
And right now she’s a teenager, and living through a developmental drive to autonomy where the bonds to parents are breaking down and she’s stretching out in the world. In more natural circumstances than ours she might have moved out into the world already.
I completely empathise with how shocking and sad this feels for you. I think it was in the movie Coda that there’s a scene where the deaf mum admitted that she felt sad when she was told her baby had perfect hearing and it really resonated for me as the mum of an autistic child navigating the chasm of experiential differences.
Sometimes it’s important to remember that any neurological condition, even the most common typical one, can be a disadvantage. In this case, your natural propensity for woolly thinking, and theory of mind are leading you to very hurtful place.
It might be more helpful (and especially through the next few years) to focus on helping your dd feel loved (and treasured, liked, trusted, respected, safe….) because love is something we experience most in the giving rather than the taking.
I’m not trying to minimise your grief - feel it, and don’t dismiss it, and don’t feel bad for challenging your dd with it. She’s also learning how to navigate this world and you’re her safe place to experiment (being the parent of a teen is brutal) but understand that there’s another way of thinking and being in the world that you cannot grasp where what she said isn’t hurtful or sad and doesn’t mean anything like you think it does. You just have to trust her. 