Hi and Welcome to the Cardiovascular Forum, 7Lil!!
It's nice to meet you, though I'm sure sorry to hear about your Mother! I'd just like to offer you info so you can understand a little more...
First of all, I have had a heart attack and I now suffer from angina, on a daily basis, sometimes very painful. That said, mine has been diagnosed as small vessel disease and is currently controlled by wearing Nitro Patches and taking Nitro sublingual (under the tongue). Though it's never normal. Sometimes there is nothing to be done by surgical intervention and medication alone controls it.
The other case scenario is you have a blocked artery, and you have angina, without surgical intervention, you have a heart attack! - or you have a blocked stent and need surgical intervention, or you have a heart attack!
So you see the dilemma here?! I do not know your Mother's specifics - is her Dr. aware of this current situation? - if not, he/or she needs to be made aware of this!! The fact that she's taking the Nitro so frequently? - That is not usually normal!!
The Nitro Protocol is 1 tab. under the tongue. If in 5 min. the pain is not gone, you take a 2nd tab. If you have to take a 3rd tab. You should be dialing 911!!
I truly hope this helps you understand and I highly (strongly) recommend that your Mother seeks help ASAP and make sure her Dr. knows this is going on, too!
I hope you are doing okay?? My best wishes to you and your Mother.