The End? Really? You are in for a very rude shock.
In looking to find medicines that will help women with orgasm and arousal problems, sexual arousal have been studied in thousands and thousands of women. A probe inside the vagina is used to detect vasocongestion and wetness in a woman's vagina (the primary signs of arousal) as various videos are played to her.
The results does unfortunately not agree with your dictionary definition. All healthy women get aroused by lesbian sex scenes. And shockingly, as much as by heterosexual sex scenes. These studies have been verified over and over, and peer reviewed, so it is no use to attack the science and techniques behind them. Most of these women does not self report that thay get aroused, yet they are aroused.
What defines a woman as heterosexual, lesbian, bisexual or any combination is not what she is turned on by or aroused by, but what she does with those feelings, and what actual sexual contact she prefers. You cannot think yourself lesbian or straight. And every woman knows instinctively when she looks for a sexual partner, what she is looking for, a man, a woman, several men, several woman or a group. It is not because she gets turned on by watching one type of porn or another. It is because it is a deep rooted preference that she was born with.
In isolation, women will have sex with women, and men with men without changing sexual preference. This is because sex is a basic need and if no other form of sex is an option, any sex will do. In recent studies, a lot more straight women are reporting sexual contact with other women. Maybe it is just an experimental phase, or they got high or drunk, but research are showing that it is happening a lot more than you would think. And these women never have another same sex incident again, and do not classify themselves as lesbian or bisexual.
Do not get confused by all this. You know what your preferences are. Getting aroused or thinking about another woman, or lesbian sex does not make you anything other than what you are. Your sexual preferences is programmed into your DNA, not your thoughts.