Sunjan,
Audio Technica makes a mono wireless system (Pro88) that works for a rather modest $170.
http://www.bhphotovideo.com/c/product/68061-REG/Audio_Technica_W88_68_830_Pro_88W_Camera.html#specificationsPRO:
• Cost
• 20-100 ft. range - mileage varies
• 2 Channels of VHF/FM to try to avoid conflicts
• Light weight
• 3.5mm 1/8" mic jack/earphone and audio output to camera
• 6 hours or more on 9v batteries
• Use AGC on the camera or manually adjust audio on camera
• It is pretty well made -- battery compartment covers are weakest point
• It works surprisingly well!
CON:
• It's NOT pro gear (despite the name)
• It's plastic, not metal (despite B&H description)
• Antenna on camera receiver (it can mount in the hot shoe) is rather long...affects balance of small cameras
but it can be mounted in other ways -- still, operator has to carry that unit WITH the camera if not ON it.
• Requires a camera with a 1/8" mic jack (or adapter cable)
• Requires an adapter cable for XLR mics to 1/8"
I've used this with lavalier mics and the Sennheiser ME66/K6 shotgun. I can't remember how it worked with a dynamic mic like the Electrovoice 635A.
It would free her up to single mic the band and have the audio fed into her camera. As long as she's recording, she's getting the audio from the wireless mic. If she unplugs the mic at the camera, she's back to the built-in microphones. It's expecting mic level into the transmitter...so if you can get that from the mix board, you're set.
She can use it for interviews and standups at the TV station if it doesn't work out for concerts. ;-)