My friends big toe has an ingrown toe nail and is slightly infected what should she do?

Professional Help.: Slightly infected nails can blossom into severely infected nails rather quickly. If the nail is ingrown, then the best solution is to have it evaluated by a competent specialist. Many times the problem can be relieved without actual nail surgery. Anecdotal remedies can often times just make the problem worse.

Infected toe nail: This is likely a paronychia. Your friend can soak her toe in warm epsom salts. Seeing her podiatrist would be a good option too.