Convictions resulting in a conditional discharge become 'spent' (other than as below) after 12 months or at the end of the discharge period, whichever is the longer. So, in this case (since the periods are the same anyway) your sister's conviction will be 'spent' in January 2012.
So your sister won't haver to declare her conviction when applying for employment UNLESS that employment is exempted from the provisions of the Rehabilitation of Offenders Act. (e.g. for posts working with, or alongside, children or vulnerable adults, or for work within the criminal justice system). When applying for such employment (or for voluntary work, such as with the Girl Guides or other youth groups) no conviction is EVER regarded as spent.
The position with regard to insurance applications is more clear cut. The conviction will be regarded as spent and she won't have to declare it.
Other than in very exceptional circumstance, the criminal record of court witnesses may not be disclosed to the magistrates (or to the jury in a Crown Court). Those circumstances are unrelated to whether a conviction is spent or not.
Assuming that your sister holds a UK passport, she won't need a visa to travel to any EU country. Many other countries either offer visa-free travel to British tourists, or never enquire about criminal convictions. However where such questions do form part of the visa application process overseas authorities don't recognise the UK's Rehabilitation of Offenders Act, so convictions are NEVER regarded as 'spent, and must always be declared.
In particular, the USA's Immigration and Nationality Act places a life-long ban on anyone ever convicted of an offence of 'moral turpitude' from entering their country. (There are limited exceptions but they won't apply to your sister). Theft constitutes 'moral turpitude' so, in the first instance, the US Embassy would be obliged to refuse your sister a visa. However the application could then be forwarded to Washington as an application for a 'waiver of permanent ineligibility'; if that was granted then the US Embassy could re-consider the application. It should be noted that the process (for those with convictions of 'moral turpitude') is extremely lengthy; it typically takes at least 5 months, with delays of up to 15 months being reported by others on this website. So, if your sister is planning to travel to the USA, she needs to apply for her visa WELL in advance of booking any travel.
Chris