I just received an update from Undine's daughter, who has given me permission to post it. She writes:

Cause of death was pulmonary embolism from deep vein thrombosis, i.e. a blood clot to the lung. Very fast. According to my friend it just feels like you suddenly need the loo. Daily Light was found on the floor next to her. She treasured that book, and despite not being Christian any more I recommend it for daily readings. I owe her 20 quid for our bet on the election, I've spent it on bulbs for her grave, going to get some help from her lovely church to go plant them.

Her daughter is travelling at the moment but she will try to check in with us here when she has some free time.

She also asked me to pass on her thanks to the anons for this tribute thread.