Executive

Before enrolling for both the course together, you must know and understand the structure of both the professional courses.
Firstly, I would like to tell you about the Company Secretary course
The course comprises of three programs
Foundation program
Executive Program
Professional Program
After qualifying all the three programs, the candidates has undergo a practical training for a period of 15 months, in a company or CS firm.
After the 15 month training, the candidate has to go through another practical training for a period of 15 days in registrar of company, Stock exchange, SEBI, Company Law Board etc.
As far as course in LLB is concerned, after +2, the duration of the course is 5 years. After completion of the course, the candidate will have to appear for an exam conducted by All India Bar Council and has to complete 1 year internship, to be eligible to practice in court.
Now, according to me, your daughter should enroll for Company Secretary after +2 and law after graduation. This will enable your daughter to complete all the three programs of CS I.e Foundation, Executive and Professional program, along with graduation. After this, she can enroll for the LLb and could pursue while going through the practical training of Company Secretary course. In this way, she could manage to pursue both the courses without much difficulties, but if she decides to pursue both CS and LLb after +2, its not advisable for better results.
Like CA, CS is also a professional course which is carried out in correspondence mode. Whereas Law will be of 5 years long regular course.
She can do like this- Taken admission in CS foundation and simultaneously get into LLB, with specialization in Corporate Law it will be much better for a CS candidate if she is opting for law with corporate law as specialisation.
But things will get tougher for her to manage, as she have to manage both CS and Law simultaneously. Clash of examination dates may also create a head ache. Besides these managing both courses will take great effort and hard work to score better. Besides this she would surely have to opt for good coaching for CS and Law if required.
So, confirm with her if she is capable to manage CS studies + coaching + Law studies simultaneously.
If not better first complete her CS, then opt for LLB (Corporate Law), it will take additional 3 years to complete LLB. If she is going just after +2 will take 5 years for completion.