a woman who is having medical problems should be througoughly evaluated by a competent physician. If she is told to take drugs with profound, dire and long-lasting side effects, or surgery she should get a second and third opinion. If her doctor merely prescribes something to abate symptoms without diagnosing and addressing the underlying cause of her problem, she should get another doctor.
No hormone therapy should be taken until a specific diagnosis of lack of the hormone or hormonal imbalance is made, and the replacement hormone should be the natural form, not synthetic, hormone that is lacking. (Diane Schwarzbein MD, the Schwarzbein Principle for this paragraph)
taking medication to the extent that periods cease entirely, as with newer versions of the patch etc. has even more, longerlasting side effects, as yet not completely studied, and is among the most drastic applications of the therapy.
if after all is said and done the contraceptive pill or patch is prescribed for a medical condition, there is no conflict with Catholic teaching, but the patient is well advised to research the FDA warnings and research about side effects of this therapy. the unmarried woman in any case is not engaging in sexual activity so there is no problem with the contraceptive side effect of the medication prescribed for an off-label use.
we can’t give medical advice here, but we can give the results of our experience, and above is mine, and we can cite church teaching, in a general hypothetical case as OP cites. for a specific individual, she needs to see a good doctor for a medical problem, and she needs a priest for a personal moral dilemma.