In many women there is a degree of stiffening as blood from arousal causes the vaginal lips to become heavier with blood flow opening the vulva somewhat for intercourse
Every woman's private area looks different. It's just like the rest of the body, we are all unique and therefor everything about us is different. This wont have anything to do with masturbating, it's just the way she looks down bellow. It is normal and when she is older and starts having sex she will find that there is nothing wrong. As for the lump it could be a number of things which aren't serious. If she is worried the only way to help is to see a doctor, telling a parent is daunting but they've been through it themselves when they were young anyways