Is a makeup or expiation required for one who masturbated during Ramadan, and she is unsure if she knew that it invalidates the fast, and what is the ruling for one for whom more than one Ramadan has passed?

The best cure for waswas (whispers/obsessive thoughts) is to ignore them. Masturbation is always forbidden (haram), and its prohibition is even stricter during Ramadan. It does not invalidate the fast unless semen is ejaculated. If someone engaged in it, unaware that it is among the things that break the fast, then their fast is valid, and there is no make-up fast (qada') required of them. However, if someone engaged in it, knowing its prohibition but unaware that it breaks the fast, then they must make up the fast. Since the questioner doubts her knowledge of its prohibition, the default assumption is that she was unaware, and therefore, she is not required to make up the fast, nor is there any expiation for delayed make-up.