I’m sure you are talking upwards of £500 if it is anything more than a smart repair, requiring spraying and blending in etc. By the time you talk about “contributions” on that, like half, you are probably into what her excess will be anyway – make her insurance pay and any premium increases are on her head! She’s not driving in a cheap banger and she only said sorry when she realised that there’s money involved (either yours or hers). If she’s in an 11 plate car and she hasn’t literally just got it 2nd hand then it’ll have cost her a decent lump of cash.
If it’s £250 make her pay out of her own pocket anyway and she can be thankful you didn’t go through her insurance.