Help for Honest Hearts DLC

So I bought the "Honest Hearts" DLC, but to start it, I need to be alone (without a companion). However, I didn’t have one with me. I checked the map and saw that Lily was near the casino in Freeside. I went to look for her to send her back home or to the casino, but she’s nowhere to be found. I can’t send her away, and I can’t start the DLC because the NPC at the start of the DLC acts as if I have a companion. Does anyone have a solution? Is it possible to dismiss companions through the Pip-Boy?