Is it weird for an 18 year old girl to still like dolls?
No, not at all. I'm a 19 y/o girl who has a whole shelf and two floor spaces for my dolls and things of the like. Never be ashamed of enjoying something like this because if you are worried about others peoples negative reactions/opinions, then they aren't worth your time. As long as you enjoy them that's all that matters.
My mother liked her dolls until she died at 98.
A lot of adult women enjoy collecting dolls, though they don't necessarily do what you do, unless perhaps they are setting up a display in their homes. Perhaps you are reluctant to be heading into real adulthood and are trying to connect with your childhood. 18-year-olds aren't quite adults yet, not matter what the law says; they're just late adolescents. As you grow older, you'll mature, and doing this may seem less interesting and appealing to you. But even if it doesn't, if it's not interfering with your normal life in some way, it's no big deal.
Not at all infact I still buy barbies for my niece that is in her 30's