I think you would be selfish to continue a relationship with her. You weren’t selfish for the stag do thing, but it seems like that to her as she’s more committed than you. I think she’s very into you and believes you are ‘the one’. It’s going to be you who has to break it off. She’ll probably say that she’ll give you space and all the things you want to hear, because she won’t want to break up. However, in her heart she won’t really believe this, she’ll just hope you’ll come around and if you don’t in s year, or two, she’ll resent you and it will be like a merry go round, you pulling away because she’s pressuring you, her resenting you because you don’t feel the same. Time will be passing and eventually there will be irreparable bitterness in your relationship. Or you will come round and you’ll move in, marriage, children etc...who knows??
The crux of the matter is that you’re both 30, still young, but not kids anymore and you are at different stages in your life. IMO the kindest thing to do would be to end it with her. Sometimes this is the wake up call people need and they end up realising what they lost and get back together and commit, or they go their separate ways and meet other people. I spent years with someone and even ended up getting married to them because it seemed the right thing to do. They never really felt like ‘the one’, although I loved him very much. The marriage barely lasted two years and he got very hurt. I should have split up with him years before, but I didn’t. Luckily this was in my twenties and I was young enough to move on, have a child and meet my now partner. If you carry on for a year and are ready to move in, then the next conversation is likely to be kids, marriage, mortgages etc. If that totally scares the shit out of you and is not something you see, or see in the very, very distant future, then as the cliché says ‘if you love her, let her go.’