Brief Answer:
Muscle spasm is the commonest cause.

Detailed Answer:
Hi.
Thanks for your query, albeit short and specific.
Throwing up once on severe pain can be a reflex vomiting that can come with any severe pain.
Severe pain in lower right back close to the spine that started an hour back can be due to one of the following reasons:
Muscle spasm being the most common cause.
Any inflammatory lesion - the pain is gradually increasing.
Ureteric colic can present with lower back pain.

Pleas give me some additional information for me to assist better:
Did the pain occur while moving, bending, pulling something, getting up or so?
Is it at one pointed spot or generalized over a large area?
Any referred pain in abdomen or lower limb?
Any urinary or other symptoms?

Please give her the following:
A PPI like Omeprazole to avoid the acidity caused by pain, vomiting or may occur due top anti-inflammatory medications.
Give her any anti-inflammatory like Ibuprofen if it suits her.
Wash off the essential oil and give hot fomentation.
Strict rest in the best position that she can have with least possible pain.

If these measures do not help much or have another symptoms as asked above, please take her to the Doctor/ER for clinical evaluation, examination and necessary investigations as would be guided by the clinical findings.

I hope this answer helps her.
Please feel free to ask for further relevant queries if you feel that there is a gap of communication; please give feedback about the questions and on further evaluation.

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Brief Answer:
Take care.

Detailed Answer:
Please give feedback.
Shall be happy to assist you further.

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