Mom is all for it but I am not sure what the FSIL’s parents think.
After being together for 3 years or so, the subject came up with mine. From the beginning there was input from M-I-L, who wanted a very large wedding for her only son. We previewed a very nice wedding venue, that could hold 500 easily. The groom's family is from a rural area where they have a great number of cousins. Certain things wouldn't work, since the venue had what I'd call bare-bones stay-over accomodations for my close family.
What then happened really made me proud. My daughter completely took over the planning, made spreadsheets, got 3-5 estimates, and made her decisions, keeping both mothers at a good distance.
There were so many great moments for me. For example, I went to help pick the dress. Lol, the shop owner told me she did not see many fathers in the shop.
He and She made some payments as the estimate grew. He wanted a 9-piece band, and paid about half of that. M-I-L kicked in about 10%.
YMMV. It really depends on the relationship of the couple. If she truly does not want "the package", then it will work for them. But our young couple wanted "the package" and it really came off as a spectacular event in freezing weather at the beach, with COVID keeping some away at the last minute. So the number dropped from 200+ to about 155 we paid for. We were in the hotel/hall for 4 days, and it made everything so simple, self-contained.
There could be substantial friction that your daughter wants to avoid, so I'd trust her judgment. But as my chart shows, parents do have an interest. So their wishes deserve some consideration, but not drive the final decision.
We, her parents, actually went easy on her family, and had a simple ceremony, with dinner for about 30. But times change, we're not our children, and they did not take my offer. They had specific wants, something like a total-entertainment blast. And they made the right choices.