So, major spoilers here: Much later in the game, after Emily initiates a thighjob in the shower, she reveals that she has a fear of pregnancy and doesn't even want to risk doing the pull-out method. Her own mother went through serious health complications giving birth to her, and Emily worries that she inherited that trait. Earlier before that, she explains that she is not ready for sex because of inexperience. With that being said, she could just have the MC use the dildo in her room if she wanted to do more positions safely.