Translation:Her attitude can threaten her future.
I agree. With due respect to Roger, it is not as simple as saying that peut=can and pourrait=could. Our idioms are different, so we say the same thing in different ways, and English speakers simply do not use the present 'can' when dealing with a hypothetical future. 'Could' is a better word here for what the French means. In fact, 'May' probably works best if you want a present verb: 'her attitude MAY threaten her future' seems perfectly natural to me (though, frankly I probably wouldn't use the verb threaten in this context. I'd probably say something like "her attitude is going to cause her problems down the road" or something like that. But keep it simple).
"attitude" starts with a vowel so you must use "son" in front of it even though it is feminine
right, it is important for us anglos to drill it into our heads that the pronoun gender matches the noun, not the owner of the noun. This could be properly translated in four ways:
1) her attitude can threaten her future
2) his attitude can threaten his future
3) her attitude can threaten his future
4) his attitude can threaten her future
And all make sense - my attitude could be a threat to myself, but it could also be a threat to my wife, for example. Or even, say, my brother (so the two 'his'es could refer to different hims.)