Be clear what you are disciplining her for.

If she has less than 2 years service then you may have more leeway, but with over two then you need to go through a fair process (as you should under two really)

You either believe she is lying (unlikely you will be able to prove it) or her level of absence is so high that she is incapable of doing her job. If its the latter then you should ideally informally warn/counsel, before stepping through the stages.

In reply to Keith:

Thank you Keith,
Do You think, if Bradford policy been implemented then such cases can lower down? what you suggest, is this policy is any good for any company or not where mostly people are working on per hour.

ACAS doesn't distinguish in its advice between "discipline" and "capability", but we tend to, here at the CIPD forums, and our distinguished member, Peter, has done a very good post about it that you should read (I wanted to supply a link but cannot find it - I'm sure Steve Bridger will be along shortly to help us out!).

I would guess that, perhaps, you don't have a sickness absence policy or, if you do, it doesn't have clear trigger points. Although small businesses generally don't need these, it can be helpful to draw a line to make decision making easier as to when action is warranted. Certainly, it should be made clear to this employee that 1-2 absences per month is unacceptable. Experiencing "stress" during probation (which should be the easiest part of a job, where you always have someone to turn to for help and you aren't expected to be 100% on the ball yet) is also not a great sign.

The big red flag, though, is that she "has some health issues". This suggests that she may have a condition that might provide her with protection under EA 2010, despite her short service. You will need to tread carefully and wait for the doctor's note before making a decision. If her health issues turn out to be nothing major, then proceed with either a warning that her absence rate needs to improve, or move immediately to dismiss with notice at your preference. If, however, she has been diagnosed unexpectedly with something chronic or life threatening then you might wish to be more humane. Whilst it is frustrating to have a new employee suddenly manifest serious health issues, how you deal with her will be noted by your other employees and you will be judged accordingly. Firing the person who was just diagnosed with cancer tends not to send great signals about your corporate culture.

In reply to Robey:

Yes, Robey - here we go...

 Conduct and Capability: Compare and contrast! 

In reply to Robey:

Thanks Robey,
This is so so helpful.
Means Alot.