there was a bit of a misunderstanding, I meant that Bella is a widow and that she knows it, not that she is in fact a widow but is not yet certain.
The only way you can push this is by saying that she directly lied about still being legally married. That is not within reasonable doubt.
Does Bella seem to you to be presented as a psychologically steadfast character?
Most of the time yes she is. She does have her bad moments, but beyond those she is perfectly normal. What you are suggesting is a constant state of delusion. That is a massive stretch.
her main scene, the one in the library after the stolen kiss, casts a fairly negative omen about her and her relationship with MC; if MC had known the truth then (which we do not yet know) he would not have kissed her but would have run for help.
Why would he run for help if Bella was simply married or widowed?
and although that scene remained without direct consequences, Bella's seizures continued and even the one she had in MC's room was not that light.
You see this is the part where you show that those are not valid reasons for her mental state. To me they are perfectly plausible underlying causes and the MC's comment is just literally him expressing he didn't know what Bella's situation was. Which he didn't at that point in the game.
Bella lied, or omitted or whatever, about college regulations is a fact, so Bella can lie
Many people consider omission more moral than directly lying and draw the line between the two. More you haven't shown how Bella was deliberately deceitful about it rather than simply inexact.
When Josy tells the MC that she is in a relationship and he assumes she has a boyfriend, she does not correct him. That was deceit by omission and even then Josy tried to argue that she wasn't lying.
Bella might consider even that as a line she wouldn't cross.
At times Bella messes around with the MC as a joke, but not on truly serious matters. She does straight up lie to Tybalt so she clearly does have some caveats like lying being okay when it gets Tybalt away from Jill. The worst deceit Bella has done to the MC is cheating at Go Strip and she even owned up to that when the game was done.
Your idea hinges on Bella either being in a constant delusional state or directly and blatantly lying to the MC. The first is a massive stretch and the second likely a line she wouldn't cross.