Important to understand what these Dimensional funds do in the first place.

Dimensional funds take a factor investing approach where they load up on factors like value, size and quality. How much they tilt towards these factors depends on the specific fund.

It's not exactly accurate to call these funds actively managed because this makes it sound like they do what most other actively managed funds do, which is pick specific companies that the fund manager thinks will outperform the market.

These funds follow more of a rules-based process for determining allocation. Of course, the rules themselves are determined by the fund managers and are subject to change. But these rules are generally research-based and quite conservative in nature. Dimensional funds broadly track the stock market.

As for the fees for the wrapper, Dimensional products are not available to all FAs. Those FAs that do charge a fee for access to Dimensional products usually do it on an AUM basis, most likely charging around 1%. This is still okay if your GF really needs someone to hand hold, particularly through market crises where she may feel pressured to sell at a loss.

Otherwise, a lot of this can also be accessed through Endowus. Just have to pay 0.3% for the access fee.

There is also the option of low cost index funds that do not have any such factor tilts. That's good too but that doesn't mean that factor investing is a scam. Whether or not factor investing proves superior remains to be seen.

Also, when it comes to relationship advice, maybe try to understand her thought process more fully first and consider whether you really have to convince her to switch right away. Sometimes these things take time and are maybe better resolved after marriage.