Translation:The girls see the spider and run away.
The first letter "bet" can't be a "vet" sound unless it's a foreign name or as an "and." I think it's a V now because it's not the first letter. There's rules about when it's "u" vs "v" for "and" but I'm learning too, so my response is based on what native speakers have said on other questions.
I hear UVORKHOT.
It is a bit tricky to hear. Especially when we cannot slow the audio. It seems the sound of the first "o" gets a bit lost between the strong "v" and "r" sounds. This occures also in other audios here.
Try to focus and listen to it a few times. Best ignore the rest of the sentence.
That's colloquial. And doesn't have the same meaning. Take off usually implies /references either a plane starting it's flight or slang as in; I'm taking off now, see you later (or: he just took off, wonder what happened)... Running away from something implies distance from that literal or metaphorical thing. Taking off, implies you're leaving a location, not necessarily because of what's there, it could be also because of when or what's elsewhere (if that makes sense, when as in: I'm taking off now or I'll be late for work..).
It is imho, because running off implies it was "away from the spider " vs the spider being a sign or landmark. (I couldn't think of a better way to say this, apologies, but: When you see the spider on the corner of 5th and Main, start running... VS girls see a spider.. Eek it's a spider, run for your lives!
Actually לברוח means "to escape" and "to run away". It is not just running as in לרוץ. The focus is more on the "away" than on the way this is done.
Sure, in English we can describe what happens between the girls and the spider either way. Imo translating with "they run away" helps to memorise בורכת and its difference to "just running". And you never know when this might come in handy. ;-) BTW I think there should be other sentences with לברוח to really get the full meaning. It occurs so rarely in duo.
Basically, the rule is that when a word starts with the letters ב, ו, מ or פ (try remember it as BUMP) or there is a shva under the first letter of the word, the ו is pronounced as u. Otherwise, it is "ve". But, note that it's not really used in everyday language, so don't worry about it.