That's the thing! Only they can come back. We can give them a safe place to come back to, but they are only going to do it in their own time. So what we get to try to do is to become the best person we can be, but it is for us, and not for them.
The last thing you want to do now is things that let her know you want her to come back. That will backfire almost every time. I've read way too many threads, and that is almost always what happens.
So, it could be that what I read is wrong, but if I see it in what you are writing, could she be seeing it in what you are doing? If she does, you need to try to stop it, I think.
And don't listen to friends who think you should be on a dating site. The are not trying to save your marriage, though they are trying to help you. I've been temped to go that way, but, as you discovered, we know it isn't the thing to do!