הכרויות דיסקרטיות|חילופי זוגות

Im (30M) I work doing maintenance for schools, theres a teacher (36F) who is extremely beautiful. I was working in her school From December To January, id see her in the hall. She woule give me a big smile and would always stare at me. I never had the chance to talk to her. I left the school in January, but last night I came back to fix a door. Obviously its summer vacation so shes not there, I saw her name on the staff picture frame in the main hallway

I found her on Facebook, but I cant add her on Facebook because she disabled her add as friend button. I can only message her but deep down I feel like a creep

Ive never done anything like this so im hesitating. Could I have advice ???

If I message her, what should I say???