I have to say that I think the focus on Besson is probably not the wisest approach. It REALLY narrows the possibilities and excludes a number of other perfectly good instruments (ranging from Chinese clones through British, German, and Swiss instruments). My guess (and I emphasize that) is that she prefers the Besson because it's probably the only decent instrument she has been able to play. But the inference from that to "I have to have a Besson" is something of a stretch.
Here are a couple of other suggestions if you can avoid being in a rush to buy a Besson:
1. There are several Tuba Christmas events in SC -- including one in Charleston on Dec. 15. See http://www.tubachristmas.com/readtcloc.php?TCState=SC for details. Go to one and see if some people will let her try their horns. Most people playing at these events are VERY supportive of young players -- and you might find some instruments for sale.
2. The US Army tuba/euphonium workshop is Feb. 3-6 in Arlington VA: http://www.usarmyband.com/tuba/. There will be hundreds of tuba and euphonium players there, and a significant number of instrument vendors (Wessex, Tuba Exchange, etc., etc.) in a large room. MUCH opportunity for trying instruments, making contacts, trying out horns, and finding some used ones for sale. And you'll be close to Baltimore Brass and not TOO far from Dillon. Plus, it's just a great experience to hear those people play. My wife and I went last year and it was fantastic. The workshop is totally free and open to the public. Parking at the conference site on base is easy. And all you have to worry about is finding a place to stay and driving around Arlington (which can be a little challenging). Places to stay range from nearby motels to higher-end hotels.
I would just caution against excessive haste and too narrow a target in this case.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)