Of course, all sorts of things could still go wrong with a flower delivery to the home. She might not be home. But again, you try to minimize the chances of this. You try to find out from her or her friends what her schedule’ll be so you can choose a date when she’ll probably be home. You maybe call her house earlier in the day just to verify this, but in a subtle way please.
And if the worst case scenario happens and for some reason she’s not there to receive the flowers, no big deal. Someone else will probably be there to receive them, and they’ll be waiting there for her to return. Although then again, the worst thing that could happen would be for the flower delivery person to get lost and not be able to make the delivery at all, but if you have them the complete address, this shouldn’t be a problem. You could also leave your number so that in case the person gets lost, you can be called for directions and guidance.