What Causes A Vaginal Lip Lump With Irregular And Hard Periods?

My girlfriend, after major life changes in her life (moving, new way of life, etc) has a knot like bump on the outside of her vaginal lip. I has been there for about 4 months now. It gets smaller and then bigger and then stabalizes to it's "normal" size before, after, and during sex. Also, as of late, her period seems to be irregular. She doesn't have med insurance, so I thought asking this on here would help possibly get some resolution to what could be going on. She is 32 years old. Always had very hard periods lasting 3-4 days and always on time every month. This month it seemed to have started on time, but went away and came back 10 days later. She is of Hispanic culture, 32 years of age, and maintains a healthy weight and diet (with occasional junk food intake). Could this just be stress and an inflamed gland on her vagina?