For low-key gravel she'd probably want a nice fast-rolling XC tire. The Conti Cross King or Race King, for example.

My initial answer would have been to put Thunder Burts on, but it seems that Schwalbe does not make them in 26 inch. They are my go-to XC tire. The CX Comp seems to look similar to the Thunder Burt.

As mentioned above, Continental Race Kings are pretty much the fastest mountain bike tire out there - faster than some gravel tires.

You're looking specifically for the "Protection" version, not the less expensive "wire" version. The skinwalled Bernsteins are the fastest, but the black ones do pretty well too.

Crosskings are significantly slower, however, they make a decent front tire if more grip is needed.

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