If you want for now, get a moisture removing agent and stick it in your truck, just so that mold doesn’t get worse, have you checked your windshield seal? That could be a issue also
Here is a link to something I was thinking of for a moisture removing tool: DampRid FG50T Moisture Absorber 4 lb. Hi-Capacity Bucket-for Fresher, Cleaner Air in Large Spaces-2 Pack, 4-Pound, white, 2 Count https://www.amazon.com/dp/B06ZXXLQTR/ref=cm_sw_r_cp_api_glt_fabc_Y1XVNE8N57EYFXFZAW7M
Go to Home Depot and get the huge monster RV sized containers of Damp Rid. If not available there, Amazon has them too: 2pk Damp Rid RV
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Yes. Buy this below and set it on the floor in front of the car seat. It will dry the air out and prevent mold. It sounds like she had a bad weather strip to begin with as a lot of moisture is getting in somewhere.
https://www.amazon.com/DampRid-HI-Capacity-Moisture-Absorber-2-Pack/dp/B06ZXXLQTR
Tub of dehumidifying crystals helps.
https://www.amazon.com/DampRid-HI-Capacity-Moisture-Absorber-4-Pound/dp/B06ZXXLQTR
Dehumidifier and DampRid