If the problem is only on 2.4 or 5...I think those are the lowband channels in Dallas.....it is most likely some sort of electrical interferrence. That is one of the mose difficult problems to find. It could be any number of things. I once had it real bad at an apartment complex and it ended up being the light that lights up the word COKE on the coke machine....it took me 12 hours to find that one. Another time it was the florecent light in someones fish tank. Start shutting off breakers in her house and see if you can get it to go away...if it does go away then you have isolated what circuit it's on and you can then start unplugging different things. Good luck.
This is CABL.com posting #172351. Tiny Link: cabl.co/mSZ1