I wonder
A feminine sentence-final particle expressing wonder or uncertainty, equivalent to 'I wonder'.
かしら is a sentence-ending particle used mainly by women in casual conversation to express wonder, doubt, or a question to oneself. It is softer and more polite than かな, and often conveys a gentle, introspective tone. You can use it when you are not sure about something, like 'I wonder if it will rain tomorrow?' or when asking yourself a question. It is also used to ask a question indirectly, making it sound less direct than a straightforward question. In modern usage, it is somewhat dated and is more common among older generations or in fiction, but it is still understood and used in casual speech.