I'm very confused - can’t get multiplayer to work on Minecraft Java Ed MacOS or PE iOS, please help!

Solution 1:

Minecraft Java Edition is not at all linked to Minecraft Bedrock Edition. If your child's friends actually play Java Edition then you will need a server to play on if you want to play together. You can search for servers online, there are plenty of server ranking sites with recommendations. They can either join one of those servers, or if they're all together in person one of them can host a LAN world and anyone connected to that network would be able to join it. You can also set up a LAN world with a VPN but that's a bit more advanced. The alternative to that is of course buying your own server.

If her friends are already playing together on a server, you can just ask them for the IP and add that as a server under the multiplayer menu for the right Minecraft version (which is usually the latest release). From there just connect to that server when her friends are playing and they can all play together.

If you opt for buying a server you'll need to give her friends that IP for them to connect to like I mentioned in the last paragraph. If using a LAN world you won't need the IP and it will automatically show up at the bottom of the multiplayer menu for them to connect to.