Dismissal without warning during probationary period?

I have a member of staff who has worked with me for 4 weeks. Already she has had a combined total of 6 days of work including sickness and compassionate leave. She is currently away again from work (ill). Although I haven’t warned her about her performance can I exercise my option to give her 1 weeks notice during her probabtionary period?

I am just really concerned that there could be potential problems down the line with this employee.

Any tips anyone?!
Chris James