How can I tell if someone is accessing my iPhone?

1paco3 wrote:

The reason that I’m saying that she has my information of my phone my password and everything how can I find out if she’s doing that

It is unlikely that this person has access to your phone. However, they may have access to your Apple ID.

In addition to the excellent articles leroydouglas linked to, see this:

If you think your Apple ID has been compromised - Apple Support

1paco3 wrote:

The reason that I’m saying that she has my information of my phone my password and everything how can I find out if she’s doing that

?

ref:

Change / Set a passcode on iPhone

Change weak or compromised passwords on iPhone

What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support