It won't affect your score at all....unless the loan defaults. In fact, it shouldn't even show up on your report. My Dad co-signed a Sallie Mae loan for me and it appears as "Individual" in my credit reports. Just make sure she doesn't default.
Scores: TU (FICO8): 781, EQ (FICO8): 798, EX (FICO8): 788
In my wallet: Chase Sapphire Preferred: 16,000 | Chase Slate Edge: 8,100 | Bilt World Elite Mastercard: 16,000 | Fidelity Rewards Visa Signature: 8,500 | PenFed Visa Gold: 12,500 | Penfed Pathfinder: 15,000 | Apple Card: 6,500 | Lowe's: 35,000 | Northern Skies FCU Platinum: 15,000 | Kohls: 3,000
Mortgage 11/20