There are at least three aspects of the difference to intercourse with and without a condom: practical, physical and emotional. Usually, only the middle one gets talked or asked about, but for the first, you may find you need to use some lube when you could 'just' use the lubrication on the condom. If one or both of you need to conceal that you're having sex, there's a different set of things to consider.
For the emotional side, there is an additional element of trust involved: you're trusting that she's taking it properly and both of you are trusting that the other one hasn't got an STI.
She's your first partner, so the only person you could have caught anything via sex from is her. If you are not her first partner, then it's possible that she may have - presumably unknowingly - caught something. Having both of you testing is something to consider.