Actually, the hymen is not inside the vagina, so inserting your finger all the way in would not break it anymore than inserting it half way. The hymen is a muscle located on the outside of the vaginal opening.
Also, many women do not have intact hymens when the become sexually active. Many things can break a hymen (intense physical activity, horseback riding, tampons, etc), so really, don't worry about the hymen. She probably doesn't have one (even if she's still a virgin).
As to the other question. Vaginal lubrication is perfectly healthy to ingest if you're both free of STDs.