That was one of my guesses but it felt, I dunno, weird considering the situation and position they're in.
I'm also not a native speaker, so my TL might be a bit off. I can elaborate a bit.
すごいことになってます
すごいこと (sugoi koto) is "amazing thing/matter/event/filler noun" and に indicates a "destination", which can be literal or metaphorical (the latter in this case). なってます is "becoming". So literally it's like "[this is] becoming [an] amazing thing[?]". There's not a lot to work with here (this is often the case with Japanese), so some interpetation of the situation is necessary.
言わなくていいから (the っ symbols are not meaningful) is a bit harder to translate. 言わなくて is straightforward, it means "not saying" (it's the negative-continuous form of 言う, which is the verb "say"). いいから basically means "because [it's] okay" but the meaning of いい is a bit more subtle than that. So together it literally means "don't say [it] because [it's] okay [if you don't]", but that's a stupid TL. The meaning is "you don't have to say that".
早く is "quickly".
So my interpretation of all of this is that Beatrice is fingering Dorthy and commenting on her reaction (getting intense). Dorthy thinks that's obvious and doesn't want her to say so (maybe because she's embarassed?). She says "quickly" because she wants to get it over with, or wants her to go faster, or whatever.
Of course, there are some leaps in that interpretation, but because Japanese often lacks context, an interpretation is required to make a meaningful translation. So the goal is to make as few leaps as possible in your interpretation while still providing a TL that makes sense in English.
Sorry, this one is just hard to understand through the language barrier!
