How to address strange author order of a collaborative paper within "equal distribution" section?
Go with your supervisor's advice, talk to the Computer Science student and ask him/her, in a very gentle manner, why the authors were ordered the way they were rather than alphabetic in both sections.  This is the norm for equal distributions.  Can't imagine what reason the other student would have to go a difference way.  If he/she does not have a very good reason, ask them to reorder the names in alphabetical order.  If they do not comply, you can always ask them, again, in an email copied to the supervisors.  At all times, exercise grace and patience - being firm but gentle gets results much more often and burns bridges much less often.
PS: be very careful if you ask that student in an email.  Written communication on what could be a negative issue, will by default come across as confrontational.  Even if you are not trying to, they will usually see it as you confronting them on something they did that was non-kosher.  So if you do email him/her, make extra efforts to explicitly communicate a non-confrontational tone.  Maybe start by thanking them for their work in the paper and telling them how much you appreciated the opportunity to work on it as well.  Make your question about author order very light, do not point out his/her name came first, just that it was not in alphabetical order and you are wondering why that is, especially since you note the advisors are ordered alphabetically.