I already mentioned that Louise would've been most easiest and safest for Lena as an option to have threesome with as she is pretty much under her thumb (or legs), while also satisfying her guilt of cheating on Ian with Louise, but Louise/Ivy/Holly aren't tagged as cheating

as "
Having sex with a girl friend is not cheating" and telling bullshit such as "
Oh! I was just preparing her for you Ian that's why i just couldn't stop having sex for you just to fulfill your you fantasy" and the threesome as a result come out of no where as a a surprise thus, proving that Louise's only existence is to be Lena's toy which can be used at her whims as Louise agrees to have sex but not only with Ian but Mark too Thus again proving Louise's only existence is to be Lena's toy

.