Bizzie,
It is considered best practice to issue a contract of employment immediately, not after a trial period. This contract should make clear all aspects of your employee's employment, such as sick pay if any, notice of termination etc, etc.
Because you employ other members of staff, she would be covered by the same terms and conditions as your other staff already, regardless of your failure to issue her with a hard copy of her employment contract.
So if you pay other members of staff sick, regardless of earnings, then yes she would be entitled to sick pay, however if you pay other staff SSP, based on their earnings, and your new staff member does not meet the rules, then no she doesnt get sick pay.
Regarding her bad back, was the incident, sorry alleged incident logged in your accident book?
You need to find this out, quickly, like others have already said, it is very easy for employee's to claim for such things, you also need to ensure that your training records are in order, has she recieved any H & S training? Manual Handling? etc, etc, again these points could make it very easy or difficult to fight any claim for compensation.
Regarding the car accident, all incidents should be investigated, and logged, regardless of the outcome of any car insurance claim, your other staff insist that she drives to fast, your own disciplinary procedures should have kicked into place in order for you to resolve this, if she did indeed take her eyes of the road to light a ciggie, and this can be proven, the words "without due care" spring to mind.
You also mentioned how loud she is, and how poorly she communicates with your customers, this again could cause major problems, if she gets to hear about this, she could lodge a claim for unfair or constructive dismissal against you.
Try DG's advice, but dont make it obvious, and inform all other staff that you will not tolerate "gossip" about other members of staff, because if this employee gets wind of any of this, you could be in all sorts of trouble.
Regards,
Rob