Referring to the friend who sends lots of emails

She emailed me last night, wanting my phone number

This phone cant do phone calls abroad, but even if it could, i have concerns about giving her my phone number

Reason is we are in different time zones, plus i work and i know what happens when she gets distressed (from when she was in uk) she will phone over and over again until i answer, even when i have told her im not available to answer the phone, thats why i dont want to be giving her this number

I think its likely she wouldnt even check what the time is here in the uk before phoning

I have already told her twice that this phone cannot do calls abroad

How do i explain without her going off at the deep end at me?