I think Bella is using Jolina. Maybe they were in a relationship at some point or maybe Bella has just been playing Jolina as well.
When she catches Jenna spying on her laptop, she mentions how she always trusts too easily and in the wrong people, naming Tommy, the MC and another person that she was about to name but doesn't. Bit of a stretch but that could be Bella.
In chapter 20, after the Jenna/Jolina scene, when the MC says 'everybody has their secrets' she looks guilty and was about to confess to something before being interrupted by Jenna.
Similarly, if you are in a relationship with her, she will look upset and ponders for a while before confirming that Elaine was the one who sent the email. If you're not in a relationship, she confirms it without missing a beat.
I think it's either they're together and Bella is manipulating her, like she tries to do to the MC, or she has got something on her or maybe she just promised her a cut of the inheritance to save her cafe.