Mom's treatment...

Hi gang. I posted here one other time when my mom needed a change in her treatment. You were so supportive and helpful, I can't tell you how much I appreciate it. (Though I'm sure you know!)
Here's our latest issue: My mom has mets to the liver and is Her2 positive. She just finished a second round of Herceptin/Carbo/taxotere. She did
great on it. Went from 18 lesions in October down to four, and those
actually shrunk.
Her onc now wants to do Herceptin every 3 weeks and try
tamoxifin, which she hasn't been on to "buy more time."
She WAS on Femara after her first chemo for mets ended last year. She
was on this for about 5 months, then her 2 lesions turned into 18.
My question: Does this mean NO hormonals will work for her? I'm so
scared there aren't really any more options for her if the tamoxifin
doesn't work. I plan to call her doc tomorrow to talk to her myself, but
any guidance you can shoot my way, I'd really appreciate.
Thinking of you all, amy