DD 16 just came home from a friend's house on the bus. It's about a 30 min bus ride. She was upset when she got home saying a man roughly in his 60s who was clearly drunk (smelt of alcohol and was swaying when he got on the bus) had chosen to sit right next to her despite there being many other free seats. She said he stared at her and made her feel uncomfortable, put his face close to her when talking to her and told her she was really pretty etc. She was trying to ignore him and looking at her phone, messaging friends etc, and said he was constantly looking at what she was doing on her phone. At one point he also touched her arm because she had turned away from him in an attempt to ignore him. She said she wanted to tell him to move away but felt too scared to do so.
I don't know what I'm posting for. I suppose I'm just upset on her behalf that men feel this sort of behaviour is appropriate especially towards a teenage girl. DD is very pretty and attracts a lot of attention from boys her own age, but this feels different and almost bordering on harassment the way she described it.
How can I advise her to manage this in future?