You clealy need professional advice regarding this.
First you need to consider the business case with regard to costs and cut backs. Maybe you need to re-organise workloads that means a particular role will no longer exist. The legal definition of redundancy is:-
The employer has ceased, or intends to cease continuing the business, or
The requirements for employees to perform work of a specific type or to conduct it at the location in which they are employed have ceased or diminished.
You then have to consider the selection pool. Say its an accountants role and there is only one accountant then that is the 'pool'. If it is say a sales rep or admin role and there is more than one person carry out that role then you could have a number of people in the 'pool'. You then need to set fair selection criteria which is justifiable and objective . Often it is things such as length of service, experience, qualifications relating to the job, absence record (excluding maternity leave), disciplinary record. Be careful that it doesn't include anything to do with trade union activities, maternity leave, requesting flexible working etc.
Apply the criteria to everyone (possibly using a points system) and see who comes out bottom. You can't just say pick her because she is perceived to be less organised, unless you have taken disciplinary action against her for being unorganised and disciplinary is one of the criteria.
On top of that you have to follow statutory procedure if you are going to potentially dismiss someone. You have to write to anyone saying their job is at risk (everyone who's job is at risk), invite for a meeting, explain it all, explain criteria, consider other roles, then tell them decision and give right of appeal (and thats if its a redundancy situation in the first place!
You could be left open to a claim for unfair dismissal if you get it wrong.
Alternatively you could offer someone a compromise agreement to exit the business. They sign away all rights to make a claim of any kind against the company for £XXXX, all agreed by lawyers and end of story. However, the second you raise it with an employee, they could say that you have undermined the mutual trust ect of the contract of employment and resign and claim unfair/constructive dismissal.
To sum it up, be very very careful