There is no back spot required. Since there is no release from her bases, there are no rules regarding what the bracer can or cannot do at all.
Even if there was a release, then the rule is that the bracer has to be in a double based prep (no spotter needed) or in a single base with a spot. That’s what we’re calling the “two under” rule; there have to be two people under the bracer on a release – either two bases or a base and spot.
The only time you must have a spotter on a bracer in a double based prep is in a braced flip.