The Innocent Victims United group has invited Tina McKenzie of NI21 to attend its victims hustings event in Cookstown.
The only Euro candidate left off the invitation list will be Martina Anderson of Sinn Fein.
Kenny Donaldson of IVU had earlier told Ms McKenzie that she couldn't be included unless she stated her public opposition to violence.
He said this was necessary to allay suspicion, because her father, Harry Fitzsimmons, was convicted of an IRA bombing offence in 1972, several months before she was born.
"I was still in the womb," Ms McKenzie said.
She added that she felt hurt to be singled out in this way, describing it as discrimination.
"He wanted me to publicly oppose and renounce violence in a newspaper interview," she said earlier this week.
Yesterday she sent Mr Donaldson an email in which she stated: "I reject all acts of paramilitary violence and illegal State violence carried out during the Troubles.
"I got into politics for the specific reason that I want Northern Ireland to move forward; that my children and all of the children of NI should never have to experience the trauma of victims and their families."
She also repeated her comments in an interview with the Belfast Telegraph.
Mr Donaldson said his organisation, which represents 14 victims' groups, was satisfied with her response.
However, he denied that he had discriminated against her, or singled her out because her father was in the IRA.
"Tina was never and will never be discriminated against by IVU... we are nevertheless content for Tina to attend our meeting tomorrow night on the basis that her comments go some way to publicly affirming her position on violence and its illegitimacy," he said.
He added that IVU already knew the position of the other parties on violence, and had asked them about it on previous occasions, but that Ms McKenzie was new to it.
However, in yesterday's paper he said: "Tina has not been involved in violence but she is the daughter of someone who was very different, and for victims there are sensitivities, and those issues have to be dealt with."
Asked if it was right to judge people by what their parents did before they were born, he replied: "To be honest, on victims' issues, yes."
Ms McKenzie has refused to disown her father but admits they disagree on politics.
At tonight's meeting parties will be asked to sign up to a 10-point contract on victims' issues.