At our school we have a 'hub' type space for student who aren't in lessons temporarily. That could be because they're having problems or it could be because of mobility. My DS was in there for two weeks when he was on crutches as there were no lifts to higher floors and some of his lessons were on them. His lessons were live streamed to his PC so he was seeing exactly what the other students saw and could ask questions if he needed to. Then the hub teacher would help him if he got stuck or he'd chat on line to the subject teacher. Worked very well. You may find the school has similar. Have you asked how they're going to accommodate your DD?
I wouldn't get her BF involved - not by asking her directly, nor by putting your proposal to the school.
Firstly, in the weeks DD is at home recovering, the BF may have made new friends which you're then pulling her away from. That can build resentment at best. At worst you could find the BF decides at the last minute that she no longer wants to push a wheelchair around and your DD is stuck.
Secondly, there's also issues around health and safety - the school may not want a child pushing another child around in a wheelchair with all the doors, furniture and other kids to negotiate around every day!
Thirdly, what happens if the BF goes down with Covid or flu for example, something that takes them out of school for a week or two? Is your DD stuck then?
Better to have a proper plan in place involving adults like the school nurse (if you have one), the HT or year teacher rather than depend on a young child.
This is for the adults to sort out and the school needs to find a way of supplying your DD with an education whilst she's recovering. They'll have had people who have been on crutches, recovering from operations or in wheelchairs before and will probably be well versed in these sort of problems.
Talk to the school about how they propose to help but don't involve the friend. She may well get involved anyway but it's not for you to suggest. It's for the school to plan.