Hey there, Losing a best friend is one of the worst things that anyone can go through, it really is, especially at a young age. Especially as it was only around a week ago, she'll still be feeling the pain from it and she will be for quite a while.
Feeling lost will be a perfectly natural emotion after losing someone close, a lot of the time after death people feel as though they have a hole in their heart that this particular person filled but because they aren't there any more part of her is missing.
This will be a confusing time for her and because this is so confusing she won't know for sure what she is actually feeling until she clears her head and has time away from her feelings to think about the situation she's in right now.
Depending on her age, it's possible she never found herself but thought nothing of it until now, this may have made her think A LOT about things in her life.
I'm sorry to hear about what's going on right now, I hope she feels better soon.
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ALLY K?