Dear LIB readers: My girlfriend said no to my marriage proposal

From a male LIB reader

I proposed to my girlfriend a few days ago and her answer to me was 'she's not ready to settle down'. What I find odd is that she's 29. How can a 29 year old lady not be ready to settle down? We've been dating for about 11 months and I thought we were at a good place that's why I proposed. Her answer took me by surprise and I'm wondering if she really isn't ready for marriage or she's just not interested in marrying me? This is confusing to me. Please help.