If you really like her then do her the favour of tough love. You are an enabler. Shoving money at any addict is not kindness. She is, you say, a spending addict.. At 60, it's time for her to grow up and tie her own shoe laces.
Any habit gets worse, not better, by sentimental indulgers enabling it. If you could actually watch her phoning her drug dealer or placing her gabling bets, as soon as you hand over the cash, you would realise it must stop.
You don't know what she spends her money on, but seem to think it an endearing little foible that she has a life long habit of squandering, and no private pension. Take it seriously. You may be so rich you have more money than you can think what to do with now, but you cannot be sure you can cover the habits of a parasite who writes blank cheques for others to meet, for the next forty years she may live on your/our backs.
Designer handbags, drugs, alcohol, toyboys, gambling, extravagance of any kind is not within her reach now her two husbands are gone. It simply doesn't matter what she is spending it on. She must live within her means. Going into re-hab will be a shock, but one she really needs.
There is an organisation (Steps??) who do people's budgets for them. Possibly CAB will, as well. There are certainly lots of people in debt, and lots of people and organisations dedicated to explaining to them the wisdom of Mr Micawber. Some of them don't go for a realism wake-up until they have become homeless and in hopeless debt which will take the bulk of their income for decades. Is that what you want for her?
Your 'enabling' hand outs are cruelly blocking her from having the incentive to pull herself together and learn to live happily ever after.
(Would it help you to imagine yourself in the position of someone whose vet warned them their pet will die of obesity, yet they enjoy giving it 'treats', and it enjoys eating, so they persist and finally kill the animal? )