A free trial doesn’t imply anything. You have the choice to test the paid functionality and if you don’t want it, the trial stops and it continues as free.
As for the account, the majority of us here are community users of Gitlab who have no permissions whatsoever to assist with accounts, passwords, 2FA, etc.
So to address issue 1, you have two choices. First is you can open a support ticket here with the Gitlab team (of which I’ve already selected for you user accounts option) https://support.gitlab.com/hc/en-us/requests/new?ticket_form_id=360000803379
The support ticket may or may not be addressed quickly since the majority of tickets are for paid users only. So you may have to wait a couple of days, which would be the same as waiting 3 days for it to self-delete anyway. If she wants to start contributing earlier than this, choose a different username/email address combo. Otherwise it’s just wait or open a ticket which may be slightly quicker.
The other alternative is continue the registration that she has already started and provide the phone number. Gitlab is a trusted and responsible company so there is nothing sinister about giving a number. If you don’t want to do that, wait 3 days.