The charities behaved appallingly, ie where not satisfied with the amount the house was sold for, they wanted more, ffs it was 2008 in the midst of the financial crash, she was lucky to find even one buyer.
I remember reading that at least one big charity (and I'm guessing that most of them do the same) had a full-time legacies officer, one of whose jobs was to keep track of the values of large bequests which might considerably change in value (such as houses) and also to assess their likely time of receiving the legacy.
Many will say that they're just being responsible and practical in ensuring continued income, but I wonder how many people who've left legacies would genuinely be happy to know that the increasing value of their home and their own ages and/or states of health are actively on the charity's radar and continually monitored from that point on until they die.
You think you've made a very kind gesture and then, when your time finally arrives, many years later, the charity will be notified, respectfully check their records, realise that you've mentioned them in your will and then start gently and sensitively pursuing their legacy, immensely grateful for anything they get.
In fact, from the moment they receive the original notification, they see your money as theirs and, if anything, you as the obstacle to their getting it (by stubbornly remaining alive). They add it to their balance sheet, to continually actively manage it along with all of their other rolled-over assets, projecting when they might expect to realise its value. As has been stated, they will then be very annoyed if they feel like they haven't got the maximum entitlement that they were planning on. 'Grateful' doesn't come in to it anywhere.
I've no way of knowing if this is the case, but it wouldn't surprise me at all if some deliberately sent annual Christmas cards or 'thank you for your ongoing support' letters to the more elderly donors of large bequests for the sole purpose of waiting for them to be returned 'addressee gone away' (quite probably to a care home or hospice, once over a certain advanced age) or 'addressee deceased' - to give them a heads-up and a spur to pounce.
One reason of many why I much prefer small charities that are run wisely and responsibly as trusts by volunteers and/or sensibly-paid employees who genuinely have a passion for the charity's aims rather than the massive ones that are to all intents and purposes just another business that happens to sell sob stories and promises rather than goods or services.