I completely understand your reservations, OP. But if you've paid for the holiday, and you can't get your money back, then why not give it a try? I was very nervous when I holidayed solo for the first time - and yes, like you, it was the prospect of dinner alone in the evening that bothered me most. So my way round it was to have a biggish meal at lunchtime when (I thought) solo eaters were less conspicuous, and then have a snack in my hotel room at night if I needed anything else. After my first couple of solo holidays I soon realised no-one was looking at me, and dinner alone isn't a big deal for me any more. But at first it was, so I do understand.
People here have suggested hostelling. If it's Australia/NZ (I don't know about other destinations on the other side of the world) then forget everything you think you know about hostelling. It's just like staying in a hotel, except that there will be shared kitchens and restaurants, with a culture of eating together and making friends - there are likely to be lots of other people on their own, all ages, and you can be as included as you want to be. When I was in NZ quite a lot of the hostels did evening barbecues which made for a lovely sociable evening. If you don't fancy hostelling, try taking some guided tours as you'll meet people that way too. You don't have to spend time on your own unless you want to.
Failing all of that, have you tried the Thelma and Louise website? There may be other women looking for holiday companions to your destination who'd be only too pleased to join you.
It's already paid for, so what have you got to lose? If you have a horrible time you can put it down to experience and not go again. But you're very likely to enjoy at least some of it.