Disney's Fairy Tale Weddings just completely overhauled the way they price weddings, and it is now possible to do only a ceremony with added cake-cutting and Champagne toast. You just have to spend $50/person on the cake, Champagne and any small bites you add.
However, a buffet meal would trigger private reception pricing. This doesn't mean your daughter has to have a traditional reception with DJ and dancing. After our ceremony in Morocco at Epcot, we did a a buffet brunch at BoardWalk Inn's The Attic with just an iPod playing background and first-dance music, and it was perfect for us:
https://disneytravelbabble.com/trip-reports/wedding/day-4b/
If your daughter decided to just do a ceremony with cake and Champagne and then do a restaurant meal rather than a private event, there is only one ceremony venue in Epcot where they would likely let her do the cake-cutting, and that's Canada Terrace:
https://fairytaleweddingsguide.com/wdw-venues/canada-terrace/
All the rest would require her to move everyone to a separate venue—inside the park or out—that may have its own venue fee and food and beverage minimums, possibly negating any savings made by doing a restaurant meal.
This episode explains the new pricing in detail, including how much the various Epcot venues cost depending on day of the week and time of day:
https://disneyweddingpodcast.com/disney-world-wedding-pricing-2020/