Alicia is not very shy in general, but she seems that way to some people because she's socially anxious. When she was younger, she was more outgoing, but now, because of the effort it takes just to function day to day, she rarely feels comfortable talking to new people, even when she likes them. That less of them making her shy and more it just being her nature to avoid strangers. She's also pretty often uncomfortable any time she has to carry on a conversation with someone new. The exception to that trend is Melissa, because she's an angel, and we all love Melissa.
She will, however, get shy when she receives unexpected compliments from people she particularly likes (not romantically, just anyone whose opinion she values.)
Alicia DOES gets flustered, specifically, when her boyfriend is unnecessarily flirtatious. Believe it or not, Alicia is actually a pretty big flirt herself (more of that coming in book 3, I promise) but the few times she's gotten flustered so far is because Kattar felt the need to be coquettish lol.
