I really do think its a very unfortunate cultural misunderstanding.
I'm in a longterm mixed-race (African/European) relationship myself and have experienced bereavement on both sides of the family.
The English side (mine) generally expects quiet stand-backish comfort, offering cards/phone numbers etc. and then retreating to allow a sort of gentle privacy.
The African side (his) phones each other several times daily, expressing emotion freely and openly, exchanging multiple daily texts, as well as emails, and the usual expected cards etc. There is a general flurry of activity around the bereaved persons.
I have become very used to his cultural way of dealing with death (but for those unfamiliar and not prepared for it, it can feel extremely overbearing and smothering), but on the flip-side, I have to be very careful and go the extra mile with his family, because they perceive quiet withdrawal as cruel, cold, and uncaring.
Even if she's been in the UK a very long time indeed, her ingrained cultural interpretations may well be coming to the fore in what is a very traumatic time for her.
If it were one of my husband's family members, I would sit her (and any family she wished to have with her) down with a hot drink and express how very, very sad I was for her loss and that I had mistakenly been expressing respect the way my own culture does, by giving space and quiet, and that I now realised it did not come across that way, etc. etc.
Basically just be very sincere and honest. Its nobody's fault, just a genuine misunderstanding between cultures in a very sensitive time.
