The term in question is phrasal verb which is defined as
a phrase which consists of a verb in combination with a preposition or adverb or both, the meaning of which is different from the meaning of its separate parts. Cambridge
When changing the tense of a phrasal verb, only the verb is affected, for the simple reason that adverbs and prepositions do not change with tense, as they are not verbs. It is also crucial to note that phrasal verbs do not come with hyphens. However, a number of them can be hyphenated or compounded to function as adjectives or nouns with related or unrelated meanings.
To use your example, the past tense of mouse over would be moused over, while the present participle would be mousing over. You could also hyphenate to make a noun, as in, "The trackball is so bad that a simple mouse-over to the top-left corner of the screen takes more than twenty seconds."
For reference, here is the definition of mouse over:
mouse (verb)
[with adverbial of direction] use a mouse to move a cursor on a computer screen:
mouse over to the window and click on it NOAD
Some standard phrasal verbs, their tenses and their adjective/noun derivatives:
PHRASAL VERB PAST TENSE PRESENT PARTICIPLE ADJECTIVE/NOUN
brush off brushed off brushing off brush-off
fall out fell out falling out fallout • falling-out
check in checked in checking in check-in
cross over crossed over crossing over crossover
drop out dropped out dropping out dropout
knock down knocked down knocking down knockdown • knock-down
see through saw through seeing through see-through
shape up shaped up shaping up shape-up
stand by stood by standing by standby
take away took away taking away takeaway
take off took off taking off takeoff • take-off
All this said, there are indeed some standard hyphenated verbs (these belong to the larger group of compound verbs, majority of which do not have a hypen, e.g. backstab, broadside, singsong, overtake, bypass, etc.), but these are not verb-preposition combinations, as you indicated. Rather, they terminate in verbs or are wholly verbal in composition. For these species, the tense change affects the word in its entirety. Examples:
COMPOUND VERB PAST TENSE PRESENT PARTICIPLE
(with hyphen)
booby-trap booby-trapped booby-trapping
flip-flop flip-flopped flip-flopping
see-saw see-sawed see-sawing
sun-dry sun-dried sun-drying
T-bone T-boned T-boning
However, there exists one (and there may be a few more) true hyphenated phrasal verb (verb-preposition) that is treated wholly as a verb: one-up
PHRASAL VERB PAST TENSE PRESENT PARTICIPLE ADJECTIVE/NOUN
one-up one-upped one-upping one up [on]
It appears, however, that this verb may be a back-formation from the original noun phrase and, later, adjective, one up.
Best Answer
While it's possible to "affect" change, it's not the intended meaning here:
Now, if she actually means to affect positive change, that would simply mean she wants to turn the positive change around (for the worse).