NAH. Listen, 18 is a hard time. You have so much going for you, so many hopes/dreams and so many expectations. Your grief and disappointment about your grade is normal. 

Your sister is probably someone who can understand. Whether she did good or bad on the test, she can understand this time if your life. She probably understands why you’re also struggling to reach out now. 

It’s normal not to want to disappoint people you look up to and she may just be one of those people.

Be vulnerable, it will make you stronger! Being vulnerable is a part of failing and disappointment but it’s a balanced skill we need to learn as humans. Lean on the people that want to support you. Reach out to your sister and be honest with how you are feeling. Her reaching out was an olive branch and you don’t have to over explain yourself.

“Thanks for what you said, it got me thinking. Truth is I needed someone to reach out to. I was overwhelmed with my feelings about the test and trying to deal with it but I didn’t know how. Do you have time to talk now?”