You know her, and the precise details of all of this - we don't. You'll have an idea of the level and intensity of contact there has been til now. When did her Grandma die in relation to her 'changing'? Perhaps her Grandma was ill, and this was worrying her?
So, she said she loves you? How quickly did you say it back? How long after this did she change?
Just be consistent and caring. Don't see-saw, going hot/cold. Don't try and get her to chase you. Not because it might backfire or won't work, but because her Grandma died and you love her. So, be loving. I think being supportive, or just offering to be supportive, is good. Trying to push her into responding (indeed, chasing) is, frankly, not very caring or supportive, and not likely to be what she needs right now. I know how easy it is to panic. Try not to, or at least to not give into it.
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Of course, it's probably quite a bit more complicated than that.
You know sometimes, between the dames and the horses, I don't even know why I put my hat on.