maxalr

I saw a few questions asking about this from others, but need clarification on a few things.

My girlfriend is flying out west to see me in May. She is connecting at ORD, arriving on United (Terminal 1) and departing on American (Terminal 3) and she has about 50 minutes to make it. I have flown through ORD a few times but I don't remember any details about getting from gate to gate, I always had plenty of time thanks to snow delays.

My question is - getting between T1 and T3 - if she takes the train, does she have to go through security at T3? Would it possibly be faster to walk and avoid having to wait in security again? How long does it take on the train between those terminals?

Thanks!