Most HS coaches use their JV team as a developmental squad. So while the wins are nice, it's more important that the girls are receiving proper instruction and are getting the repetitions in. The dilemma here is that pitchers are aways under stress to produce, and if the team isn't winning will feel that she's letting them down. Saw pitcher a couple years back that KNEW if she let the other team hit the ball it was going to be extra bases, and KNEW if she walked a batter that they'd eventually score unless she could shut everything down before. She became so worried about being perfect that it began to affect her on the mound and at the plate.
You'll need to watch for that and try and head it off. Encourage her to look for improvements in herself and her team. Help her analyze her mechanics and her pitch selection vs situations (sometimes it's not that it was a bad pitch, it's the fact that it was thrown at the wrong time). If she's comfortable with the team, encourage her to let them know that she's trying her best, and she that appreciates their efforts on her behalf (might encourage a few of her team mates to start working on being better at the plate or in the field - you can't be run ruled if you hit as good as the team you're playing).
Bottom line is this is a team sport, and while pitcher can carry a team for a while, if the other players aren't there for her, the end result will be failure.