Dreams are reflections of the dreamer's feelings about their waking life at the time of the dream, as opposed to visions of the future. Pregnancy is one of the most common dream symbols. Here's a link to its definition on this website:
dreamdoctor.com/component/dreams/?contro...task=details&id=1466 Without knowing anything about your friend or what was going on in her life when she had the dream, it's hard to say what caused her to have it. Frequently, pregnancy dreams are reflections of the dreamer's sense that the person who is pregnant is about to "birth" a new life, career, relationship, etc. Babies in dreams are also symbolic in dreams with a related meaning. Here's a link to that definition:
dreamdoctor.com/component/dreams/?contro...&task=details&id=121 Being that you are in your 20s, this is a time when lots of new opportunities are growing and born.
As for the fact that it was storming at her house, that probably relates more to her life. Here's a link to the meaning of a storm in a dream:
dreamdoctor.com/component/dreams/?contro...task=details&id=1805 It reflects her sense that there is emotional turbulence in her waking life.
The great thing about dreams is that knowing how you feel about something can alert you to issues that need to be confronted or in some cases avoided. You might want to ask her how she felt IN the dream. Feelings IN dreams are never disguised, so how she felt IN the dream is how she was feeling (at the time) about the subject of her dream.
Hope that proves helpful.