I don't think a lot of context is needed, basically a girl having an intimate moment and talk with her boyfriend...
我慢しなくていいです
人を好きになるとよくばりになるって 今はわたしにもわかるから
Rough translation: (You/we) don't have to hold back, because (the expression) "To be in love with someone means to be greedy for them" is understood by me now as well?.
It seems to me that the sentence makes perfect sentence without も , so is it there for emphasis of some sort? If it means "as well", would the [as well] refer to how there are many people (boyfriend included) who understand that "To be in love with someone means to be greedy for them" and she is saying that now she is one of them too? Or does も have another meaning/function here?