Selena Gomez's Mom Transported to Hospital Over Selena Dating Justin Bieber

Selena Gomez's mom got so worked up when she found out how serious things are between Selena and Justin Bieber, she had to be taken to a hospital ... TMZ has learned.

Law enforcement sources tell us police went to an L.A. area hotel last week to do a welfare check on Selena's mom, Mandy Teefey, at a family member's request. We're told she was taken to a nearby hospital to get checked out, but not under a 5150 hold -- instead, she was voluntarily transported for treatment.

Sources with direct knowledge of the incident tell us Mandy had a heated convo with Selena that day about the reunion with Justin. When Selena revealed she and JB were in couples therapy, Mandy flipped ... realizing the relationship was going to be more long-term than she thought.

As we've reported ... Justin is a huge trigger for Selena's family, some of whom say they'll never forgive him or accept him for what they think he did to her years ago.

Mandy was released from the hospital the same day. We're told she's giving Selena space to figure out what she wants, but the fam already knows what they want ... and it ain't Justin.