I agree with Fatma. Budgies who have been in a pair almost always need another friend their whole lives.
Also, since she'll be spending more time alone because of the cat, this is another good reason to get her another friend. I'm so sorry to hear about Bijou
Because quarantine lasts 5-6 weeks, if you get her a friend now, she will have moved on from grieving and be ready to accept the newcomer and you will get a chance to bond with the new guy.
Best of luck! Keep us posted and I hope Sky feels better.