The reunion had apparently taken place soon after she had broken up with her ex-boyfriend Andy Jordan.
Spencer revealed to members of the Chelsea clan that he and Louise had spent an evening together, which the brunette beauty immediately denied.
Louise and Spencer
The self-confessed lothario broke the news to Andy first, saying that he had something to tell him that he probably wasn't going to like.
"Louise and I hooked up after Phoebe's party and I sort of always thought it might happen," said Spencer.
"I didn't go out of my way for it to happen. I didn't mean to hurt you. I've had really fun times with you. She's going to be furious. She loves you so much."
Spencer later added that he could prove it as he still had her dress in his bedroom.
The heartbroken Andy looked close to tears as he replied that he would probably never speak to Louise again. Later in the episode, he decided to confront Louise.
"Because I've lied before no one is going to believe me," said the pint-sized reality star, referring to the last series when she denied sleeping with Spencer after the pair broke up.
"I've wasted six months of my life with you," said Andy, showing no sympathy.
When Louise's brother Sam has a word with Spencer, saying it wasn't fair to make up lies, Spencer retorted with, "Your sister is a pathological liar."
Andy and Louise
Louise decided to have it out with Spencer herself at the end of the episode, calling her former boyfriend "a sick fantasist".
"If you ever want to speak to me again you will admit to everyone that you have been lying," said Louise.
"Are you joking?" said Spencer.
Louise then stated that it was "disrespectful" to make up that they had spent the evening together, adding, "You're a sick fantasist. This is obviously in your dreams that you would love to do that."