£50 for train tickets? Did she book first class. I only paid £46 return from Derby to London and back a couple of months ago by buying a week in advance and only travelling out of rush hour hours so I'm pretty sure it would cost £50 to travel from 45 minutes away if she bought them at least 5 days in advance
I also don't see the problem with a regular paying the cost on his next visit either rather than demanding he pay now even though he was in an emotional predicament with a very sick father.
I had to cancel bookings earlier this year when my father died and the client who was on his way didn't ask me to compensate him his travel costs as like most people he understood family come first
Tell her if she sends you the unused tickets for that date you will reimburse her but that her attitude has lost her a regular well paying client.
Regs are our bread and butter and keep us going through quiet periods so to piss one off over this is slightly mad
I could understand her attitude about not waiting if she had not met you a few times before but as someone who has visited a few times a little leeway should have been a natural reaction even if it did piss her off the fact your father was very ill should have been enough for her to show at least a little empathy