cardboard VS Geyser

Are you mixing up PaperMC with Fabric? PaperMC indeed is a fork of Spigot that is performance oriented. Fabric is a Modloader just like Forge. Fabric does not have plugin capabilities, since it is Mod based. There are Projects, that aim to add plugins to Fabric, like Cardboard, but these are still a work in progress. As you can see by their Progress Tracker.

I play strictly vanilla Minecraft, and use paper to host my servers, so this may be out of my territory, but I do remember Cauldron being popular for Forge mods and spigot plugins, so maybe give this a go?

The two pinned issues on their github show how much has yet to be implemented. Just as an example, here's the list of events and see how many are unchecked.

I believe it's a mixin conflict between Create and Cardboard: https://github.com/CardboardPowered/cardboard/issues/350

As for Spigot plugins on a Fabric server, Cardboard does work, though it’s still in beta and incomplete.

Use Cardboard: https://github.com/CardboardPowered/cardboard

Some more detail on how the server internals will work: The server is a based on Cardboard which allows both fabric mods and bukkit/spigot plugins to run at the same time, along with datapacks of course. The server has a wide variety of lag reduction and bugfix mods, as well as some rudimentary anticheats to prevent xraying and other blatant unfair advantage hacks

Cardboard exists but from my experience it can be buggy: https://cardboardpowered.org . Use at your own risk!

There's a mod for Java servers that allows Bedrock players to join as well. https://github.com/GeyserMC/Geyser

Geyser: Download Geyser

Geyser is a plugin that you can install on your server to enable crossplay. You can download it from their official website or from their GitHub page. There are different versions of Geyser for different types of servers, such as Spigot, Paper, BungeeCord, Waterfall and more. Make sure you download the version that matches your server type.

She plays bedrock edition on her iPad. MacOS only supports Java edition. You need something like Geyser to play together or use software like Parallels to install windows on your Mac so you can play bedrock.

geysermc is a plugin that allows bedrock players to connect to Java servers https://geysermc.org/

In case you're willing to give it a shot, see: https://geysermc.org/

Its a plugin called GeyserMC that lets Bedrock players join Java servers.

Geyser: Geyser is a proxy that lets Bedrock Edition players join Java Edition servers. It supports most Java features and cross-play between different platforms. You can use it as a plugin or standalone proxy. You can download Geyser from here and join their Discord for support here.