Is it all clients or just that one?
If it's all of them, I would suggest incorrect cure of the topcoat. Are you using the correct lamp?
If it's just one I would suggest its the dye from new jeans, new leather handbag, new gloves, or something similar.
The scuffs to the fore finger suggest she's been cleaning/working, or as per option 1 above, the topcoat wasn't fully cured.