To have changed my password?

[pimmsperfecto]

I have an account with one of the on line companies which supply train ticket. DD, who is 23 and does not live at home any longer, knows my password, as I have let her use the account in the past, for example when she has been visiting us, or travelling to her sister's graduation.
At the weekend, we were texting and she said she was going to visit a friend in X. Later on that day i received an e-mail confirmation for a ticket purchase to X. It wasn't expensive but she had used my account to buy it.

I changed my password to stop it happening again, although i didn't query with her direct whether she had used the account. I thought it was probably DD who had used the account, although I didn't immediately twig that it was the same destination she was going to.

She sent me a text later that day to ask if I had changed the details as she couldn't get into the account to check her ticket reference. I sent her the reference and said that I had changed the password, and she said why had I done this, as she had paid for the ticket with her card (it was only £5-£6). I said I didn't know if my account had been hacked as I had no knowledge of the transaction. I also sent her the new password, as I didn't want her to think I don't trust her.

She said that my explanation was untrue, that I must have known it was her as she had told me she was going to X, that I must have thought that she was using the account without permission, and that I had changed the password to 'keep her out'.

I have tried to contact her to say I love her, but she has not replied.

Do you think I was being unreasonable to change the password in circumstances where she used my account without telling me, given that any previous use has always been expressly authorised, evn if she paid for the ticket herself?

[LurkingHusband]

YANBU for adhering to the T&Cs - which will almost certainly prohibit sharing login details.

On a wider note, it seems very few service providers that operate an online presence understand how the modern world works - with most accounts having a 1:1 mapping with logins, meaning you have to share logins.