Can anyone recommend any good lightweight bicycles?

[Michael V]

I am looking to purchase a lightweight bicycle for my 58 year old mother for her birthday. She is currently using my old mountain bike which is way too heavy for her to mount on her car and drive to a trail. I was hoping someone could identify places to purchase lightweight bikes and some good brands i can look into for her. they do not necessarily have to be womens bicycles just lightweight enough for her to be able to lift onto the bike horns on her trunk without any assistance. If people can suggest bike brands and shops, that would be great. Also im a student right now so please dont suggest a 10,000 dollar bike, lol, the cheaper the better. thanks all.