This, and also don't use remote engineering until you reached level 5 since it doesn't improve reputation / access.Have you got the appropriate level of rep with her?
i.e if you bring her up on your engineers panel, what grade access do you have?
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If it only says grade 1, you need to do some more level 1 upgrades or sell exploration data to her.
Also that one. I totally forgot about that. You also can't do experimental effects via remote.This, and also don't use remote engineering until you reached level 5 since it doesn't improve reputation / access.
I think it's 3 rolls of grade 1 to progress to grade 2, 3 rolls of grade 2 for grade 3 and so on.
Once you have achieved grade 5 typically grade 1 needs only 1 roll, grade 2 needs 1-2 (this is where RNG is applied), grade 5 needs 5 - 7 rolls depending on how obsessive you are(TBH more than 5 adds very little in most cases so check the % improvements before another roll)
Further reading https://elite-dangerous.fandom.com/wiki/Engineers