Thanks for your post and welcome to our community.
Is your partner leaving us or joining us?
If she is leaving all she needs to do is give the STAC to Three and they'll get in touch with us to close the account and we'll advise on any final bills or charges. Please advise your partner to only use the STAC when they are ready. We also have the option of a PAC code which can take a few days to go through but you can advise us of your 30 days notice that way.
As long as the STAC has only been requested for your partners then this would not impact your account in any form.