
I'm no expert but I would NOT recommend injections and pills. They will increase the risk of pyometra and cancer. When I was a vet's assistant a few years ago in France, we would strongly discourag people to use these. The doses of hormones are so massive, unlike our human pills, they can't be good in the long term. I don't know how it is nowadays, maybe things have improved, but 5 years ago or so, they were nasty.
I agree with other people saying that pyometra in such a dangerous condition that it might be worth taking a little risk to prevent it?...
But then, who am I to say that? I have a very precious GR boy who, a bit like you, represents a lot to me because of what we went through together, and I've never resolved myself yet to put him under general anaesthetic...
Thankfully in France (where I'm from), we were able to take Xrays without knocking dogs out, so he's never needed it, even when he broke a toe a few years ago or when I had his hips checked (not officially, but just to give me an idea. Not breeding him anyway). He even had his teeth cleaned (tartar) while fully awake, he's such a good 'un. I know I was lucky to be working with a vet then who let me do all this!
When I came to the UK, he hurt his paw in the first couple of months and I remember going to the vet's and ask how much an Xray would cost me in case I had to check that nothing was broken, and they told me he would need to be under GA! I couldn't believe it - I'm now more familiar with English Health and Safety craziness! So I decided against it and just rested him and used homoepathy instead. Obviously, it was nothing, and it turned out fine otherwise I would have gone to the vet's of course.
But, basically, what i'm saying is, I understand how you feel 100% and if you feel too worried about it, then don't put yourself through it. I've come to feel that what matters is what you have NOW, as your own terrible life experience has probably taught you too. She's here with you now, just enjoy it, and when her time comes... But no one wants to think about that!!! Sorry about the cheap philosophical rubbish, but I find it works for me.