I'm sorry you're dealing with this again. And I tend to be conflict-averse, so I get it. But I think it's worth bringing up to see if it changes rather than leaving or just putting up with it. If she responds poorly to your mention of it, then I'd consider leaving.

Maybe it would help to focus on the disruptions that affect you the most or the ones most under her control? Like is it starting late? If it's starting late, that could be a time-management issue from the session(s) before yours, so she should be able to manage that. Also, does she make up the time at the end of session? If not, that's not really fair to you. If so, that could still be a problem because it's taking up your time.

The phone or doorbell? (Though she may not be able to help the doorbell being rung--I suppose if it's a delivery she's expecting, she could try to place a note outside saying not to ring the bell. The phone, she could put on silent or turn off (if it's a landline, she should still be able to turn off the ringer, or else get a new phone where she can turn the ringer off. And the cat--she should be able to just shut the door, and if the cat tries to come in, oh well (or shut it in another room during session.

Maybe try to put the focus on how it's affecting you. Like, "When I'm in the middle of talking about trauma (or whatever topic), hearing the doorbell or hearing your phone ring is very jarring." Or how it makes you lose your train of thought. Or "When you start late, even though you give me extra time, it affects my work schedule" (or whatever schedule it affects, even if it's just that you have to waste time waiting for her to be ready for session to start that you could be using for something else). Or even just that you prefer the frame of starting on time, which is completely reasonable.

That could help rather than framing it more as what she's doing wrong. I hope it goes well and she's receptive if you do talk about it.