Sounds like her juniper is older and growing unevenly. You could tie up the outer branches to the inside ones and then reshape. Usually when a juniper die in the center, it does not grow out. They are touchy shrubs and can burn easily over the winter on any given side and it won't grow back. Think "lightly" when trimming them...

This isn't going to be an 'easy fix'.
There's too much weight on the branches, which are causing it to open. We as homeowners tend to trim our shrubs using a technique called 'tip pruning'. That is, using electric shears (invented, by the Devil) or manual hedging shears. By cutting time and time again over the same tips, you develop heavy growth on the 'outside' of the shrub, while the inside dies out, creating a sort of 'shrub shell'.

You need to 'open' the plant, and allow sunlight to penetrate into the juniper, so that you get more growth in there. That will thicken up the plant and eventually solve the problem.

You should remove some of the weight from the edges.

The bad news: It will probably ruin the shape of the shrub for 4-6 or more years as you 'recover' the plant. Does the customer want that? probably not.

I'd find out if she "LOVES" the shrub first. Tell her it's aged past its prime, that the pruning is the cause of the problem, and that it might take years to fix the problem. You might then recommend that you can remove it for her, and replace it with a better choice of shrub for that kind of pruning, or if she'd rather have the same, you can do that too. You might loose her if you ruin her shrub, but if you give her some options, you might turn into her hero.

Good luck
I hope that this helps