I was too soft to have my beloved border terrier, Holly, spayed. At 11 years old, just before Christmas nearly 3 years ago, the vet found a lump in her mammary tissue during a check up after her booster. She had an operation to remove the lump and was spayed at the same time. She never recovered properly from the op and died exactly a week later, the day after Boxing Day. I was, and still am, heartbroken. Then the insurance company refused to pay out anything at all, as it was in the vets' notes that I'd been advised several times to have her spayed.
We got a tiny JRT a few months after we lost Holly and she's now two. I've put off having her spayed, again because I'm too bloody soft, but I've now come to my senses and she will be spayed next month. I couldn't go through all the heartache again with an older dog, new dog, Tilly is still young and very fit, although still tiny and I really believe it's the best thing to do for any bitch.
Sorry this was a bit long and rather sad, but I hope it helps prevent another poor bitch and its owner from going through what we did. So, yes, OP, please get your girl spayed, for her sake.