The stretch marks take place because huge muscles stretch the skin, and when they lose that muscle mass, these stretch marks remain. Also, many bodybuilders will bulk while off-season, and then they will lose quite a lot of mass for a competition, which will also cause stretch marks appear.
However, if you just want to cut and tone up, being a female I would rather recommend you to use SARMS instead of steroids. First of all, steroids are not meant for fat loss. SARMS are meant for this goal. Yet, they are very safe for a lady, and they will not cause any of the side effects associated to steroid use.