I am pretty sure the 'instant rapport' between Ava and Estelle is a deliberate ploy on Ava's part. All the housemates were hoping that Ava would form an 'instant rapport' with them 'for some reason' (ie. That Ava, before lockdown, would have identified them as the most popular with the public and wanted to form an alliance with them.)
They hate that it is Estelle. Josh met Ava confident of adding another houri to his harem, now he fears the Angie/Estelle/Josh thing might be making him unpopular outside the house. Ben and Layla are put out that she isn't so especially keen to know them (although they were pretty much determined just to use and evict the intruder anyway), because it means they might not be as popular as they thought they were outside the house.
Ray is a big suprise for me - I thought he would have made some attempt to hook up with Ava, but he is cringing in the corner.
This nasty habit of mixing the footage gets to me most when I am watching Ava. A lot of what I am seeing seems to be the day the housemates met Ava and the day after (Monday and Tuesday). There must be people other than Estelle and Josh (eg. Zoe, Ray, Brad, possibly Michael) who have not consciously excluded Ava and yet they have not been screened interacting with Ava. I suspect that Big Brother is showing us the Estelle-Ava BFF storyline and obscuring another storyline to show next week, giving the impression that any non-Josh relationship with a guy took place only after Ava's bestie bit the dust.
I don't think Ava's pairing up with just one housemate (and a nominated one at that) is such a dumb move - it makes her look threatened rather than a threat, it protects her from being used as the most acute angle in a 'love triangle' between George and Layla, or Josh and Angie, or having Ben team her up with Ray, Brad or Michael.
Best of all it sends a clear message to the housemates "From what I saw on TV, the only one of you that won't stab me in the back is Estelle." And they know for a fact that is true.
As for her degree in communications, she could probably construct a mythos, establish a theoretical framework, interpret a Caravaggio, know when to go for 120 pound gloss, mood-light a soup can, identify the structures of production in a cultural economy, utilise appropriate research methods for qualitative data, and participate in the post-production process.
I guess it might help her to bond with Michael - they might be the only two housemates that are likely to know much about the institutional history of film and television. And, if she were told to write an essay in the naughty corner, who knows but Ava's might be more lucid than Micheal's?