Steve, do you have an out of hours number to call your diabetes nurse for advice?
This is how I'd deal with it, but I'm not a qualified healthcare provider so it's only my opinion and not necessarily the correct advice. I'd inject the Novorapid, as that has been missed and needs to be injected to cover the food she's eaten otherwise her readings will go high. The Levemir has been done too early but only by a few hours. I'd inject the remaining 5 units of Levemir at bedtime when she usually injects the Levemir. Keep a close eye on your Nan as she may have a tendency to go a little low this evening as the Levemir has been delivered a little too early.
Are you absolutely sure she injected Levemir instead of Novorapid? You don't want to go and do another rapid injection if she's already done it but then got confused and thought it was Levemir that she'd done. If you're in any way unsure you could leave it an hour and see if her readings go up higher than they should, if they do then that would be reassurance that she indeed has done the wrong insulin.
Perhaps see what other members think, I'm not sure if this is the right advice, just my thoughts on how I'd handle it.