Subtle definition of 喜欢
One correction from the original sentence: 


  喜欢她就主动一点儿， 机会是不 会 自己跑到你面前的。


It means: if you like her, you should be proactive / take initiatives, since chances wouldn't run for you automatically(implying she wouldn't call you first). 

The sentence can be paraphrased as: 如果你喜欢她，你就主动一点儿， 机会是不会自己跑到你面前的。