I'm not a physician or a pharmacist, but I'm a long-time diabetic.
I have read that mixing lantus
with any other insulins can result in unpredictable results in both the lantus
and ... your daughter's case ... Humalog. Unpredictable can mean that the Humalog will not peak as expected (may be delayed) and the lantus
may also have a diluted effect.
Watch your daughter carefully for adverse effects. All should be fine by the time tomorrow rolls around.