Error in submitted online fiancé visa application - help!?

[Johngriff]

We have made an error on a fiancé visa application (for my fiancé coming to UK) submitted online and my fiancé has her biometrics appointment on Tuesday. We have just realised that
- We gave details of one previous expired passport but didn’t give details of the one before that, that expired still within the last 10 years and so should have been listed
- We selected ‘passport retained by passport issuer’ in error for her previous passport that we did list but she still has this passport
We're kicking ourselves for the mix up - can we edit/add to the printed out application form before she goes for the biometrics appointment on Tuesday? or do we need to withdraw the application and request a refund because of these errors? Will they have already started processing this application as it’s completed online?
Please I’d be so grateful if somebody knowledgeable can advise us what is best to do?

[Casa]

You can amend the printed version with the correct information.

[Johngriff]

You can amend the printed version with the correct information.

Thank you so much that's such a relief! Really appreciate it.