If CL balance is available, she can avail it after returning from ML. No issue, provided it's not elapsed as per their leave policy. CL is meant to be availed in emergency situations, unplanned travel, sickness, etc. Normally, a maximum of 2 or 3 days is permitted at a time, and that too not prefixed or suffixed with EL/PL or ML.
Understanding CL Policies
CL is a kind of leave not followed uniformly by all employers in different sectors. What's familiar is one type followed in government and quasi-government sectors. Some private firms/companies, micro, small, medium, may not have this facility at all. However, maternity benefits are different and stipulated by appropriate legal frameworks.
Carry-Forward of CL
Many establishments that follow CL normally don't allow the carry-forward of unutilized CL at the end of the calendar year. At the same time, where the delegation of power is vested in top officials/HODs, it's usual to have a few days of CL left by the EOY, which could not be availed due to pressing exigencies. In such a situation, the remaining CL balance may be permitted to be added to the OB of EL as a special case.