The regulations state that a hardship event for medical expenses must meet the following criteria:
Expenses for (or necessary to obtain) medical care that would be deductible under Code Section 213(d) (determined without regard to whether the expenses exceed 7.5% of adjusted gross income);
Deductible under 213d would mean amounts that the participant could deduct on Schedule A of their tax return. Publication 502 specifies that you may deduct medical expenses for "qualifiying relatives"
A qualifying relative is a person:
Who is your: Son, daughter, stepchild, or foster child, or a descendant of any of them (for example, your grandchild),
Brother, sister, half brother, half sister, or a son or daughter of any of them, Father, mother, or an ancestor or sibling of either of them (for example, your grandmother, grandfather, aunt, or uncle), Stepbrother, stepsister, stepfather, stepmother, son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law, or sister-in-law, or Any other person (other than your spouse) who lived with you all year as a member of your household if your relationship did not violate local law, Who was not a qualifying child of any taxpayer for 2012, and For whom you provided over half of the support in 2012.
I would double-check with your plan document provider, but if the participant meets the above requirements, then it seems it would be a hardship event.