I'm possibly leading a girl on
What makes you think you're leading her on?
Because I was taking her out for dinner for Valentine's day, and then I changed my mind.
Well, I'd definitely say that sounds like you're leading them on!  I think it's cruel if you're making this person think you like them when you really don't.  You should be upfront about your feelings!
I just don't know if I like her the way she likes me, I did like her more at first though.
Well, it seems you are not sure so that is a big red flag. Be open and tell her you are confused about your feelings. It only means you and her both are open to others and dating them instead which can be fun.