So, to recap: She likes to take her rig in spite of the hassles transporting it and finding real estate on stage because of its awesome tone (even at low volume settings). You prefer using a rig that is easy to transport and has a small foot print and find the Fender bass tone works just fine. You have gotten tired of the hassles with her rig and, after 'some' discussion, she is willing to entertain other options.
Your tone preferences and priorities are pretty different. The alternative amps in your first post are indicative of what you hope might satisfy your desire for a more hassle free amp and her desire for that JBL 215 tone. They are relatively small like your Fender, but have a little more power and are fairly low in cost. Its next to impossible to cop that JBL-215 tone on a tight budget, and in a compact package. Your going to have to spend more (or buy used) and go a little bigger than you want, but smaller than what she wants. In addition, you will need an amp with 2 channels or a box (pedal or small box) to mix the two signals. You evidently don't need a lot of power or spl capability. You will need a cab that produces that JBL-215 tone, but in a smaller package. Your going to have to go shopping/auditioning. We can make suggestions here for a short list, but be aware that you will get everything from 'can't be done' to 'just use this 30w 6 inch modeling amp'. As a start, look for a 212 with vertically stacked, neo drivers (narrows the cab and provides better dispersion - you can hear it better on stage too) and with modern light weight construction. High power handling is not needed. It would help us if we had a better handle on what she likes about her tone. Is the 'smile' on the Hartke's graphic eq what she likes (pretty scooped), and is there something she doesn't like - what is it about the sound of the Fender that she doesn't like?