Well, I wonder if someone could just have a conversation with you and do a voice recording that is out of your sight. You feel comfortable just talking. And perhaps this could be done outside this garden, at home, and do a voice-over type thing. Even your aversion to being photographed, you could probably manage a couple still photographs at this garden and in this video, also include still shots of MIL while your words play in the background. Another thing, just have a conversation with someone while someone else is filming, and as you relax, start discussion about your MIL, then cut out the rest of the conversation on this video that is irrelevant later, when the video is being put together. Just writing it down, practicing, repeating, and memorizing might help.