If your sister in-law has an iPhone that's probably the culprit right there that's affecting the receipt of her text messages to your Android phone. 1. If she has an iPhone, ask her if her iMessage is on when she texts you. iMessage is only compatible to other iPhones and not other brands she sends to. 2. Is she sending you text messages using the iPhone emoji keyboard? letter accents? or in a different language other than English? this could be the problem when the different cellular carrier interprets the data and sends it to your Android phone that does not have the same compatible software. Ask her to send you several test text messages in plain text without accents, no special symbols, and no emoji's. If this solved the problem, then you know what went wrong.. If you are still getting garbled text messages even with her iMessages off, and she is just sending you standard text without any symbols, icons, or pictures.. then it could be another issue.. Call your service provider to see what could be wrong.iPhone: SMS messages may display incorrectly on other devices:
https://support.apple.com/en-us/HT203428 i would suggest calling on a different phone so that you will be able to troubleshoot the phone in question while talking with Tech Supportin the US, the major cellular companies are:AT&T Wireless Customer Support: 1-800-331-0500Sprint Wireless Customer Support: 1-888-211-4727T-Mobile Wireless Customer Support: 1-877-453-1304Verizon Wireless Customer Support: 1-800-922-0204