さっさとカジノから出てってよ
私たちまで貧乏に見られたらどうしてくれるの?
From context, the character lost all his money so the girls he was hanging with say this. I can gather it's "get out of the casino. What do you plan to do if even us are seen as poor?".
I can gather is "appear poor" but why 見られたら is used?
It's the passive version of (誰かが彼女達を)貧乏に見る = "(someone) sees them as (being) poor". The particle に has various uses, so sometimes its meaning can be ambiguous. In your sentence, "to be seen by poverty" makes no sense, so there is no ambiguity in practice. In other cases, however, the same phrase can often be interpreted in two ways, and you must determine the meaning based on the context. For example, 女に見られる can mean both "to be witnessed by a woman" and "to be mistaken for a woman" depending on the context.
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