I'm dealing with some TV character's lines that speak in slang, and I don't understand what is the meaning of this "～てりゃ" in the following sentence:
Here the context:
There are three girl in a classroom. The first girl tell to the second one that she must act more seriously. Next, the third girl say the line abovementioned, in defense of the second.
I was thinking, may be that "ってりゃ" a simply variation of "ている"? And if it is so, which is its origin? And, have it a special nuance of meaning?
May you help me to understand? Thks in advance!