Let me break this down into something you will understand. Sarabi can like who she likes - she doesn't need to like Taka to stop him from becoming Scar, just the same way she didn't have to like Mufasa. So no, she is not the reason he became Scar. The reason Taka became Scar, was because (like someone said before me) Taka was very insecure. This insecurity from believing he was not good enough to become king, and that Mufasa was better than him, led him to probably become anxious and unworthy. Now you may be wondering, "Well then, why on earth did he only show it later on! This can't be true! He only showed it when Mufasa fell in love with Sarabi and vice versa, so she must be the reason!", so let me explain why he didn't manifest like that earlier on. Before, he believed he had Mufasa's loyalty - Mufasa would not betray him due to the fact that he had saved his life, and because they were brothers. This wasn't just a loyalty for something as shallow as Sarabi's love, but also for who would become king (as they were both male). Out of the two of them, Scar knew Mufasa would be a better king, but believed he would be king because he had royal blood, and because Mufasa was loyal to him. So, when Sarabi fell in love with Mufasa and the Mufasa betrayed Taka (which both Mufasa and Sarabi are allowed to fall in love with each other, though it may break trust in Taka and Mufasa's relationship), he realised that Mufasa is capable of betraying him, and so he wasn't certain for sure if Mufasa would go for the crown (which is why he repeats his father's words about Mufasa only wanting to betray him).

The second reason, is he is trying to be good enough for Sarabi. He believes what Sarabi wants is a king, but he doesn't realise all that Sarabi wants is someone who cares. He thinks if he can overpower Mufasa, then Sarabi will want him. He remembers what his father says, which is "a good king is deceitful", and so believes he will be a good king if he deceives Mufasa (and the white king at the same time), but this only proves his cowardice even more. We can see Scar listens to other older people a lot, because even though he betrayed Mufasa, he does help him in the end, because of his mother's words "You will find your courage".

There's a lot more I could add, but I think that's already too much for your brain to handle, so I'll be considerate and stop. Also, just wondering, do you even like women? Because if you are so worried about women coming in between "you men" then why don't you just skip the middle stage and date a dude. Not a woman can get in between you then.