30-30 150 gr will be fine. Keep the sessions short, it is better to go back than to over do it and develope flinches and a general dislike of high power rifle shooting. IMO recoil and muzzle blast are unpleasant sensations that become more and more fun as a shooter gets used to it and sees results. Best of luck with her, I think you are going about it the right way. Keep it fun.