So I have this sim who had a girlfriend, but was also romantic with another girl. Unfortunately, his girlfriend has seen it (him, his girlfriend and his other love interest are all in the same club) a...
@Huiiie_07 If one of them or both have writing skill (level 4 is required, I think), they can write each other love letters on the computer. This will increase their romance bar without them interacting directly. I like to use this method as I think it's very sweet and romantic :)