I agree with the others, she needs to see someone as soon as poss...unfortunately YOU know this, now you have to convince her!

Try showing her the article that Saram linked to.

FWIW I have had horrible swelling all through my PG, it isn't necessarily a problem; but having said that my BP has always been fine. It is the combination of factors that causes concern. They are looking at BP, swelling and also protein in the urine.

I understand her not wanting to be admitted to hosp, but really she has to see that if there is a problem it will not go away just because she ignores it.
It is entirely possible that everything will be fine but it really is better for her to get checked out JIC. It is much too serious a problem to take the chance with - if she won't do it for herself, then at least for her bub.

Good luck