Firstly, it seems difficult to obtain such tests from an internationally acknowledged institution (Oxford Placement Tests are used at my University) as they are usually unpublished to be re-used.

Secondly, determining your student �s proficiency level (A1-C2) seems a rather abstract undertaking as these levels are rather globally and therefore loosely defined (cf. CEFR). What EXACTLY is A2? There are no word lists an A2 candidate has to know, nor is there a list of grammar chapters or conversation topics he or she should be able to handle correctly.

Moreover, a student can be more advanced in Reading (e.g. B2) than in Speaking (e.g. A2), which would mean that you should have your student tested in all 4 competence domains. 

Regarding the online placement tests (just google for them), I am not very sure about their quality or reliability either and I would rather suggest that you design your own tests in case you really want evaluate her language skills.

Particularly if you don �t prepare your student for an exam, what I think you should do more than a placement test is a so-called Needs Analysis. What are your pupils objectives language-wise, what does she need to acquire (ask her!) and how much time are you going to take to teach her a unit/grammar chapter/topic-related vocab and so forth. 

Also try to trust your intuition and your evaluative competence and have a random chat about an everyday issue with her (small talk). Or try to make her write a short text about her hobbies or her family. 

I think this way you will very soon obtain a really accurate overview of her skills as you know exactly what you have asked her to do by designing the activity on your own. You will feel what areas you should train with her and I would repetitively advise you to trust your feelings more than any of these abstract theoretical European language concepts.