How/where are they breaking? This will give you some idea of how to help resolve the issue. I'd prefer to find out why rather than apply another product to 'fix' it.
How long have you been using IBX on her? I found it made my nails brittle so they split more after a few applications. I have very thin, ridged and bendy nails naturally and I've discovered over the years that need need quite a bit of flexibility or they split at the sides of the stress point.
It may be that the client is suffering from brittle nails too now, depending on how/where they are breaking, and that IBX at every appointment is unnecessary and maybe she needs it at alternate appointments or even once a month.