Her parents say she is sensitive and needs praise and encouragement, but you say she has gaps in her knowledge.
Some suggestions:
Assess what she knows and doesn't know. Give her an oral written assessment of the skills she needs. Make sure she understands that you need to know what to teach her.
Make the parents your partners. Tell them you are happy to encourage and praise her, but she also has to learn the material, which is hard because she has gaps. Tell them about your plan to assess her and ask them to encourage her to approach the assessment without worry so that you can best figure out how to teach her. Ask them to encourage her to be comfortable saying I don't know and also to be comfortable when making mistakes.
Give her opportunities to succeed. This will be easier to do once you have assessed her. Ask her easy questions that she can answer.
Praise and encouragement should be for effort not for success.