Any success mixing Levemir with Novo Rapid?

My daughter currently takes a mix of NR and NPH in the morning.  Nothing at lunch, but dinner is 2 shots, 1 of NR and 1 of Levemir (this is a change - we use to just take NR at dinner and then a shot of NPH at 10pm).  This switch is to avoid a late night shot.

Our doctor told us that Levemir works best when not mixed.  BUT she also said that if we're getting the control we're looking for we can try mixing it with NR so that my daughter only has one shot at dinner instead of two.  I'm nervous to try but would LOVE to have the insulins successfully mix.  This would benefit my daughter huge.

Any first hand experience?

Cheers and much appreciated :-)