Hello, Stephanie! Thanks for stopping by the Disney Parks Moms Panel with your question!
My daughter has always been very tall for her age and is often mistaken as older than she is. However, we've been visiting the Disney Parks with her since she was 18 months old and have never had a problem bringing her in when she didn't require a ticket (under 3 years old). A Cast Member may ask your daughter's age at the gates, but that is generally the only delay you will have. If you are particularly concerned, feel free to bring along a copy of her birth certificate although you are very unlikely to need it.
Your daughter is at such a fun age to bring to the Disneyland Resort. There are many
attractions that she can ride and lots of
characters that she might love to meet, including princesses at Royal Hall in
Fantasy Faire. Depending on her height, there may be some additional attractions with height restrictions that she will be able to ride like Mater's Junkyard Jamboree that has a 32" height requirement. I suggest measuring her, with shoes on, before you visit so you know just how tall she is and what attractions will be available to her.
I know you guys are going to have a magical time at the Happiest Place on Earth! See ya real soon!
-Linda M.