One day solo trip to Dublin - suggestions?

Hi all, I (26/F) am visiting Dublin in May for one day (flight lands at midday and I leave the day after at 2pm). I'm planning on moving with public transport, I've already booked the train on the second day to Belfast, but i haven't booked anything from Dublin airport to the city centre, should I? My hotel is near the O'Connell Bridge.

What would you suggest for me to do? I know about Temple Bar and the Castle, which i definitely want to see, and I keep seeing about the Guinness Factory, but my problem is that I don't like beer, so I don't think it'll be worth it?

Also, I'm travelling alone, is it a safe city? Would i be able to go out in the evening, or better not?

Thank you for any recommendations!