How do I tell my fiancé that her spending is unsustainable?

Currently 28M my fiancé is 26F. We have been engaged for a year now. We live in Sydney and she is a school teacher, and I’m a software engineer. She makes about 85k a year and I’m about 130k a year. <br><br>Our living situation is a 2 bedroom apartment in a very nice suburb of Sydney and we have saved up enough to buy the apartment (we are about 12k away from having a 20% deposit). <br><br>For the past 3 years, we have managed to save about 30% of our income after tax. So, this past summer we decided to live off my income and not touch her income at all and instead just save it. We opened a separate bank account called the sunset account. We put her entire income in that account and we just used my income for all living expenses. <br><br>During these 3 months, we did not really feel like we had to sacrifice anything, and we actually felt like we had more disposable money. And after the 3 months, the sunset account had over 40k in it. <br><br>I want to use this money for a deposit on the apartment we are currently living in.<br><br>However, my fiancé does not think that we should buy this apartment. She says that we can get a better apartment for cheaper in other parts of Sydney and we should wait it out for now. However, I believe that this apartment is priced correctly and it would be a good investment to get in now before the prices skyrocket. <br><br>I don’t know how to approach this subject with her. I don’t want it to seem like I’m saying she can’t afford the things she likes to have. But, at the same time, I feel like we are going to have to have this conversation eventually. I’m not sure if I can keep living like this for the rest of my life. I want to start a family soon and I feel like we are going to have to start cutting back on things soon. And I’m sure she will not be okay with that. <br><br>Any advice on how to approach this subject?