To answer your question, no I don't think her outing you would be considered a failure to conceal, unless she was using the satement as a threat. You do however have a bigger problem than that.
Lucky you didn't get in trouble, you probably walked by a 30.06 sign going into the ER. I haven't seen a hospital yet that doesn't have one on every door.
PC §46.035. UNLAWFUL CARRYING OF HANDGUN BY LICENSE
HOLDER. (a) A license holder commits an offense if the license
holder carries a handgun on or about the license holder's person
under the authority of Subchapter H, Chapter 411, Government Code,
and intentionally fails to conceal the handgun.
(b) A license holder commits an offense if the license holder intentionally,
knowingly, or recklessly carries a handgun under the authority
of Subchapter H, Chapter 411, Government Code, regardless of
whether the handgun is concealed, on or about the license holder's
person:
(4) on the premises of a hospital licensed under Chapter 241,
Health and Safety Code, or on the premises of a nursing home licensed
under Chapter 242, Health and Safety Code, unless the license
holder has written authorization of the hospital or nursing home
administration, as appropriate;
That is found on page 40 of your Handgun Laws
It is amended on page 41 requiring them to post a 30.06 sign. I'd be willing to be there was a sign though.
Be very careful with that one. You don't want the trouble that can come along with it. You said ER , so I am assuming you weren't at a regular DOc's office which can be different.
Carry safe and carry when and where you can. I'm just sayin'.