My question involves criminal law for the state of: Texas

I have 2 friends that were handcuffed in Walmart because they were "caught" switching tags on camera. 1 was let off with a ticket and the other was arrested and spent a night in jail. She didn't admit it to anyone official (but she did admit to me that she was guilty.) However the officers said the camera caught her "fidgeting with items in (her) cart". I wouldn't say that's actual proof so can she still be charged? Also a friend of hers who works in law enforcement (I believe juvenile officer?) informed her that because she didn't walk out the store, pass the registers, or try to pay with a switched tag they had no right to search the store and arrest her. Is that true? This is her first offense and we're both very worried that she will get jail time.

She was arrested for: Theft- 100>750 and scheduled a court date

Just trying to find out everything we can and figure out what her best options are, please provide as much info as you can. Also if you need more information just ask. Thank you in advance!