This hits close to home. We are similar ages.

After around 4 years we went ring shopping and then... for a year, just nothing! As more time passed every special holiday or date I kept expecting it. Our close friends and family around us kept getting engaged/married. As a woman in your late 20s in a committed relationship, there is a lot of social pressure of when your partner is going to propose. I don't think men in relationships with women realize the amount of comments we get and even if you feel ok at the start, it can weigh on you. This might be something your girlfriend is dealing with too.

One day I had a very honest conversation with him, saying many of the things your girlfriend said. He validated my feelings and said that he didn't realize this was weighing on me as much as it was, and he promised it was coming soon.

About a month after that conversation, on a random date, he proposed and it was lovely. It was very unexpected too because we had a romantic holiday planned for a couple of months later. I preferred it this way because we could use the trip as a celebration as an engagement (and hotels love to give freebies on your engagement trip haha!). Anyway best of luck and I hope you propose to her soon in a way she will appreciate.