1. Will she get frisked and questioned when she gets here? How long could it take and what documents does she need to get in?
She may be frisked when she goes through security, but I wouldn't think immigration would check her out. All she really needs is her passport w/ the visa in it, but she may be asked about when the wedding is to take place, etc., and could be asked about funds if you won't be married for a while.
2. Can she leave the UK in March on the Fiancée visa and will there be a problem re-entering the UK?
The fiancee' visa is good for multiple entries so she shouldn't have any problem coming and going.
3. How is Duty paid on goods - including things like a computer, monitor, accessories? How is the duty calculated, how is it paid and does it affect items that are shipped and sent FedEx?
If she's bringing/shipping in personal items that she's had for more than 6 months, there won't be any duties to pay.
8. How soon can she get a NI number and does that allow her to visit the Doctor and get such things as contraception, painkillers etc?
Technically, she can apply for an NIN as soon as she starts looking for work, but many JobCentres won't let you set an appointment until you've actually been offered a job. The NIN has nothing to do with health care. She can register with the surgery you attend and they'll arrange for her NHS number to be sent to her.
9. What is the next process to go through on arrival - is it to obtain an FLR?
She'll apply for FLR once you're married. She can apply by post (£330) or in person (£500) in Croydon, Birmingham, Liverpool, or Glasgow.
10. How soon can she legally obtain paid work?
Once she's obtained her FLR, she can work. She can't do any type of work (paid or unpaid) until then.