Ok, my thoughts would be:

1) Log it with easyJet as a complaint in writing (not over the phone).

Keep it clear there are two/three elements to this:
(a) Being denied boarding (and attempting to resolve the matter then, but not being given any thing).
(b) her general manner and rudeness,
(c) taking a picture of your passport on why you fear may have been a personal phone (it might not have been).

Right now, I would focus on (a), only mentioning any elements of (b) in so far as it is relevant to (a) about how you couldn't sort it out at the airport then and there.

(b) and (c) can be addressed later.

Focus on the facts.

You are a passport holder of X, advised Y by Spanish immigration, so booked with easyjet, you were denied boarding: Not given a reason in writing (or any clear reason at all) for being denied the service you have booked and paid for.
Not provided with accommodation, etc. Do name the staff member, and give times as best you can.

2. Ask them over the phone (referring them to the email complaint in writing) if they will be providing you with transportation.

3. how did you pay, notify your card issuer.

4. Contact sussex police and try to obtain details of the officers who were present at the time. (unless you have their details already).

5. If the answer to 2 is a negative, book yourself a flight back with another airline. Check their policy for passports and visa requirements (Airlines can impose higher requirements than countries).