One way to make it "click" for her is to get one of those dolls that drinks and wets. They come with their own potty chair. They have them pretty cheap at Walmart. At Walmart or Target, have her pick out some underwear she likes. Buy stickers, juice boxes (about 12), and a small yummy treat (like m&m's).
Plan on spending one day to really focus on this. Set up her potty chair in her play area. Put on her panties and show her how the doll drinks and then pees in her potty. Read her some potty training books (check them out from the library). Start giving her juice boxes so that she has the urge to go a lot for the day. Tell her that when she feels the urge to pee (or poop), that she can pull down her panties and go in her chair, just like her doll! When she puts her pee/poo in the potty chair, put a sticker on a chart and give her an m&m. Keep this up for the day - she will get the hang of it by practicing it over and over. It will be a long day, but she is definitely at the right age to get it.
Once this initial day has gone by, expect some accidents. If she's having more than one accident each day, then her body may not be physically able to do it yet. Being able to hold your bowels requires developed muscles. Some kids develop slower than others. So, you could put panties on her for a few hours each day (when you're home with her) and do the sticker/m&m reward system for her successes. Otherwise, keep her in a pull up while she is having accidents.
Never shame her or punish her for having an accident. You do not want a child to start holding their bowels out of control. They start getting constipated and having a lot of stress around having to go. Keep it fun and give your energy to her success, give no energy to her mistakes - just clean it up and remind her to listen to her body so she can put her pee and poo in the potty just like her doll.
If there's a character from tv or a movie she really loves you can have a friend of yours pretend to be "Dora" or "Barney". When she goes in her potty for the first time, tell her that she gets to call Dora! Call your friend and have her talk to "Dora" all about her success. (This has really been a motivator for some kids).
Good Luck! Let me know if you want more help with this. I'm a parent coach. Visit my site for more parenting support at www.noblemother.com