mistake #1: do not ask if they want to go out on a second date while still on the first. Wait a few days, then call her.
Mistake #2: Do not ask ridiculous questions. We do not know how you acted during the date, if there was any chemistry......and so on. By me giving you an answer is just me speculating.
If she is shy like u said, she's not going to tell you no right to your face. So basically, by you asking her then, it did nothing for you. Women would much rather shoot u down on the phone rather than in person. Wait a couple days, then call her.
By u asking this question, you reak of desperation. I used to be like you. I had one date every few months, and I analyzed every little interaction with the girls. Don't do this, you only end up hurting yourself.
Lastly, you said she was a very shy girl. Did you get her to open up at all to you ? B/c if you came to the conclusion she was very shy after your date you probably didnt make her feel comfortable enough. If you did everything you could, and she was still super shy, you have to evaluate if seeing a really shy girl is really worth your time. WIll they be the most fun for you? Do they deserve you ?