Hello and welcome.
You deal with a poly breakup in a very similar way to a mono breakup only you have someone there to commiserate with, support and be supported by rather than wallowing in that pit all by yourself.
You go forward, each and every day, you do your hobbies, spend time with hubby and other friends and family, you grieve, you move forward. Eventually the pain will lessen and you'll be able to think of her without the tears and pain.
There are as many ways to do polyamory as there are people practicing it!