When Trish felt out of control, she kept busy, and tried to find things she could control. And this was definitely a situation where she felt out of control. So as soon as she found out there was a place working to solve this mystery, she wanted in, even if they hadn't made any progress. It made her a little nervous that they were a PI organization - that was Jess's work, not hers - but she needed to be doing something. She was a little worried that Jess might be there, but a little hopeful, too; after all, it wasn't Trish's decision to avoid Jess, and any possibility of making things up to her was a positive in Trish's books.
When Trish arrived at WAMM Investigations, she wasn't sure what to expect; the only PI office she had seen was Jess's, which she was fairly certain was hardly typical. She had messaged Veronica to let her know that she was on her way, so that there wouldn't be any surprises. When she arrived, she hoped to find Veronica waiting for her, but if not she would wait in whatever waiting area there was. Although she wouldn't mind running into Jess later, that wasn't the main reason she was there, and she wanted to make sure that Veronica, who had offered to show her the files about the Dome, was the first one she saw.