Agreed! OP, you're not describing the heart flutter of a crush, you're describing a panic attack. You're fixating on her so much, your subconscious sees the situation as a threat and is putting your body through a simulated near death experience. Problem is without an actual threat to work through, it's just unpleasant.

Strongly recommend you look into resources for dealing with social anxiety. You're currently only reacting to her presence, but if you keep on, you'll react to the possibility she might be present, then to the memory of previous reactions and eventually you'll just have this reaction every time anyone sits next to you anywhere and it will ruin your life.

Source: diagnosed with generalised anxiety disorder and suffered through escalation for decades before I knew what was going on. On the bright side, it's fixable. You just have to put in some effort.