OP, you sound lovely.
Your poor colleague has returned to work, as people often have to, and after loosing both parents in such a time frame, you are trying to be sensitive to her, and those fondest of her are being especially kind where she works.
I think its really lovely.
Of course a good colleague would go in and commiserate as they try on concentrate on work.
Not easy after a bereavement, not to mind two.
I think the 24 year old, (who is uninvolved with this grieving colleague, who is upset in the privacy of her own office)...... is a rude CF and I would be very, very tempted to pull her aside and tell her that her callous unasked for opinion has triggered YOU.
Oh and I absolutely would cross her off.
She needs slapping down firmly, I would be tempted to have a word with HR.
Talk about an empathy bypass.🙄
Some people think the whole world revolves around them.
Not everyone can afford to take 6 months off to grieve.
Some people have absolutely no choice but to go back to work and try and carry on as best they can.