HD, in the middle of that last post, I think you got it. She may have lacked the assertiveness and interpersonal skills to say that she was getting too many texts. Remember, one of the things that Borderlines can do is be accomodating to the point their own comfort levels are affected. (....Raises hand...)
Wow, about going to group. It probably will be weird. In fact, I would prepare for that. You may want to consider coping ahead and wrap your brain around radically accepting her and the situation as it is. You know this person better than I ever could, so from a mind of radical acceptance, what could you say in response to her, or how could you support her, or even give her her space -- and still be true to yourself?
Remember, if this becomes an issue to the group, and yours and the group's healing, it has to be addressed. I don't remember what it is called. But like you said earlier, it may boil down to you or her moving to a different group. And, if you can work through this whole thing, and still stay in the group, imagine the incredible personal growth you will have gained!
You've got at least the weekend before the next group session. Remember, you have access to all the skills. Sounds like you have homework!
As far as the non-existent after hours access to your T, that's disappointing. Personally, I have no qualms about calling my state's crisis hotline. The counsellors there are very good, and they have helped me when I've decompensated. My hope for you is that they are just as good in Canada.
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Dx: MDD, BPD, Complex PTSD, Moderate Bi-Polar I, Fibromyalgia, Chronic Kidney Failure Stage 3
History of Migraines
Spinal Fusion at Cervical 5-7
Rx: Currently - Latuda 80 mg, bupropion 300 mg, hydroxyzine 50 mg, lisinopril 20 mg, Cymbalta 90 mg, counseling.
Past - Imitrex, Fiorcet, Ergostat, Zoloft, Lamotrigine, Oxcarbazepine, Abilify, Paxil, Celexa, Pamelor, Soma, Norco, Flexeril, Diclofenac, mirtazapine, trazodone, lithium, DBT group & individual therapy.

Ain't that the truth?!?