My understanding was that it's necessary to do in order to see the lesbian scene, so i'd say yeah.
have you done all the scene with Julia before?
42.Go to Pool and catch mom. Continue scene till the end (Julia catches mom giving a BJ to Jason).
43.Join Julia at pool and talk about incident.
44.Talk with mom in Dining room
49.After mowing a lawn "Ask for glass of water" will apear (need Emma 40+ score), she will invite you inside. While she was gone for glass of water click on TV (make sure you have spycam in inventory) to set up the spycam. Come back next thursday same way and you will get the video003.
50.Show video003 to Billy at school, he will recognize the person in video.
59. Make sure you have Video003 in inventory (you can download it from PC in Jason's room) and show it to Julia at living room (scene there she is sitting with her phone).
60. Catch Julia leaving her room in the Hallway and lie her about mom (to succed you need to have 80+ score with her).
61. Hide in the closet in her room and wait. You will see the scene mom-julia scene. Make sure you have finished scene at pool there she cathes mom giving BJ to Jason(42 43 44).
62. Come to Julia's room at 20-22 hours. You will find her standing near the window in a lingerie. There will be 50% chances mom to appear and join you. Make sure you have condoms and lube.
63. Go to bathroom while Julia in jakuzzi. She will offer to join her. Make sure you have lube in inventory also completed the anal training (39).
75. Repeat the evening scene at julia's room and have sex with her (if started a new game in 0.07 you can skip this step).
76. Catch Julia in living room crying. Comfort her and she will takes you to her room (having condoms is optional).
77. Repeat the FFM scene at julia's room (if started a new game in 0.07 you can skip this step).
78. Catch mom at pool, now Julia won't be mad when catches Jason with mom. And mom will let to fuck her. (condoms are optional).
If you have done all the scene and still can't act maybe the score for Julia is not enough to act the scene.