Saint Nikki of Meriden, as she is also known, caused mayhem in UKIP when she declared war on Nigel Farage using members as cannon fodder and allegedly encouraging a young member of staff to misuse UKIP membership lists to create fictitious accounts on the members' forum to post pro-Nikki and anti-Farage comments. In the end, she had the whip removed and was banned from using the UKIP name. She was expelled from the party but sued to have the expulsion overturned and due to a clerical error, UKIP's defence wasn't submitted in time and she was awarded a default judgement and allowed to rejoin.
Sinclaire of course has no hope of being elected as an independent MEP, hence forming her own political party. She still has very little chance of being elected but may dilute the eurosceptic vote enough as the fake eurosceptics in Libertas and No2EU did in the last EU election to allow the vote-splitting Tories to scrape by ahead of UKIP, setting back the eurosceptic cause.
There is no denying that Nikki has done some fantastic campaigning against the EU and she did some great things in UKIP but there is no cause more important to Nikki Sinclaire as Nikki Sinclaire. It's understandable that she would want to protect her political and financial future but for someone who pontificated on putting the cause before your own interests when she was still a UKIP MEP, it's pretty hypocritical to launch a rival political party that can only damage the eurosceptic cause. On the plus side, it's grounds for kicking her out of the party that not even an experienced litigator such as Saint Nikki can sue their way out of.