You might try a Star Valkyrie in the 165-167 or so range. I've found my Star Valks in that range to be very overstable relative to other Valkyries (and the flight numbers). If possible, physically check the disc and look at the PLH.
Someone mentioned the Viking, and I agree with that idea. Try an inexpensive DX first, and if she likes it, you can "upgrade" to Champion later.
Last, as an idea for discing down: try the TL or TL3. The TL (especially when fresh) doesn't turn over much if at all, and the TL3 (which comes only in GStar) is a bit faster, less glide-y, and won't turn over unless you "help" it to.
As ever: JMHO, YMMV.