I would say she did not want to play postflop against a bully BB big stack which would call her too often with marginal hands trying to put her out of the pot so she decided to raise more that standart 2bb raise from the BU: from now on I would put her on a middle made pair of 66, 77, 88 or (rarely TT) and a weak or middle A. The flop is quite bluff provoking and BB decided to check here which I think is justified in case he didn't have a made hand coz he did not have much fold equity on such a board against a preflop raiser. So it was actually better to check/raise for the purposes of driving the opp out of the pot.
I am pretty sure 99s would have bet here oop for value and to give bad pot odds for the draws or high cards.
As to Jen position we would not want to swell the pot holding just high cards coz we will be often called by opps with high cards and value hands thus we would rather bet or raise on the turn which is a cheaper version of bluffing . Consequently, I think Jen was convinced that she had the best hand so far so was compelled to make a value bet which will be called by K or A high (sometimes Q) or fd. BB raise otf looked like a bluff catcher and her confident reraise proved that she already had a made hand. I would exclude A4 after her reraise because just why we want to triger fold equity when we have a great equity. Ace came otr but I think Jen need not to be afraid of it because A would likely have bet given the previous action plus we see a multi flush draw now. Jen decides to continue betting but I feel like she didn't like the A that is why she bet so small.
9 comes on the river and BB checks which indicates that he was bluffing otf most likely holding a draw (K9s+, rarely Q9s+ or JTs) coz value hands would miss the chance to gain more. Jen checks which says she does not have a nine (A9), ace or 4 as well.
With that being said I would put her on the range 66, 77, 88 (probablly TT). May be someone will come to a more precise answer but if I have to guess just 1 hand, I would stick to sevens (you know what I mean

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