My SD has gone very LC/NC with us due to a disagreement 3 years ago.
Her siblings, my DC had nothing to do with the disagreement but have ultimately been cut off too by default.
They both have their own phones and she bothers to text very occasionally, never calls.
For instance DS1 hadn't heard a thing from her since a text in Feb. DS2 even longer.
She text DS1 this month to ask what voucher he wants for xmas. Last year she asked them both and never sent a thing.
I have stayed out of it but it upsets me she treats them this way. I do think you reap what you sew though and she will realise one day that the bond they shared is weakened at best.
AIBU to think that you can't just send a voucher once in 3 years and think that's keeping a relationship going. DC don't even miss her now and she knows virtually nothing about their lives, only second hand info from my MIL. They've changed so much in 3 years. It's really sad.