In Steins Gate 0 the following conversation happens between the protag おかべ and a character ひやじょう
比屋定さん… どうして ここに…
えっ？ あ いや つい勢いっていうか…
The context is, that okabe visited his friend だる in their usual hang out place the “Future Gadget Laboratory”. While おかべ is talking with だる, ひやじょ comes out of the shower, which おかべ is very surprised by, since ひやじょう wasn’t really a regular at the place at that time, and doesn’t understand what she could be doing at the place with だる.
ひやじょう calls it 勢い, in the english translation it is translated as “impetus”.
I know that 勢 can mean that,
But it even then, I don’t really understand what she means here. In other contexts, I have seen 勢い mean doing something on impulse, or getting carried away, but how would that fit into this context?
Which meaning of 勢い is being used here, and what kind of information does it exactly convey?