One thing I (and my daughter) will not do is answer ANY unidentified number or text. If a number is not in our contact list, we don't answer. If we get a text from an unidentified number, we do not respond.... even with a who is this. If someone wants to reach us badly enough, they will leave a message with name/number and we will gladly return a phone call.
Neither of us are hiding anything from anyone, we are protective with our cell numbers.
Now to your friend........ she needs to dump #2 who sounds like he is as crazy as #1. I hope she sees the red flags #2 is waving at her for being so possessive and borderline controlling. She should not have to "get through" anything to #2, she owes him ZERO explanation or proof of what she is doing on HER phone.
If #1 continues to harass her, she needs to contact the police (non emergency). See my Example below.. that worked for us.
EX: My daughter had an issue and a kind officer paid someone a phone call from the police dept with us standing there in front of him and told the person who was harassing my daughter that we were there with him at the time and charges would be pressed if any call or text came through to her number and was traced back to said person. Never had another whimper from the caller again.
At this point, your friend is possibly facing 2 stalkers.
Best wishes.