Bigger,
"You could ask your husband for time. Ask for 3 months for you to change."
Except it will take her husband YEARS to work through this. He won't be anywhere near ready to make a decision to remain with her after just 3 months (if he doesn't just divorce her that is).
And she won't be able to come close to changing within only three months.
Not many way wards do this, but they should if they really want to remain with their partner. They should divorce and then keep working on themselves and dating their ex, if their ex will let them, and then try to start over anew.
She's nuked her marriage, it's dead and gone so if they are to remain a couple, a new relationship will need to spring up out of the ashes from her carpet bombing of the relationship they used to have.
There is no quick fix for this, none whatsoever.
She'll need to be able to handle his emotional roller coaster that she's put him on too and not all people have the makeup, the intestinal fortitude to do that. Many become defensive, say it was 6 months ago, it's time for you to get over it and move on.
I have no idea if OP has the intestinal fortitude to do this for years and years while her husband tries to move beyond this.
If the OP really wants to show him she's changed, she can based upon her actions over time.
She needs to take actions, get herself to counseling, read books, be completely 100% honest with him (so many can't, they are embarrassed, they want to save their partners from hurt yet they hurt them more by not fully disclosing etc.).
She needs to do and do and do some more.
She needs to write him a 100% complete timeline. She needs to be able to answer questions of his, even repeats over months and years without blowing up at him or becoming defensive.
If OP wants to work on this, she will, she doesn't need his permission as she's the one who needs to be doing and doing, not him.
If OP really wants to fix this, her focus CANNOT be on saving the marriage. Her focus needs to be solely on working on herself, on figuring out how and why she was capable of this. She needs to work on identifying, addressing and resolving the issues she has.
Many way wards don't do this, or they quit doing it once their partner divorces them. If they really cared, they keep working on themselves. Their partner, even if they become an ex, will see that.
I'm not going to admonish her, but she needs to really begin working on herself and doing and doing and doing some more.
It's actions, not words. It's learning what she did to him, what he's going through. She has no idea of the pain she's put him through. She can't, she's not been in this position, in his shoes so a good deal of the work she needs to do is to learn about those things too.
She can't even begin to make a dent inside of 3 months.