It would have been better if you could have provided the date and time for your GF.
Someone who has Jupiter and Rahu in same house have guru-chandal yoga. In the girl's lagna chart here, Rahu is in 7th house. 7th house presents kinda legal bindings which is your marriage as well, foreign trades etc. Rahu is a negative energy whose thirst is never satisfied, it wants more and more and more. So Rahu in 7th house will exhaust their partners and get bored and will look for more. Jupiter will still try to curb Rahu's tendency so it will try to curb Rahu from cheating but yes still there is a strong possibility of cheating with this placement. However which sign and nakshatra Rahu is sitting might indicate whether you will have a good life with this person if you two marry. Irrespective, Rahu in kama house is indication of more than one relationship. Placement of Rahu in 2nd house in navamsa chart is interesting as well. Its the house of your family, savings as well. Rahu in second house wants wealth and status a lot, like hell they want wealth or status or both, will do anything for wealth or status or both. And these people lie a lot, sorry friend.

If you are planning to marry her and she ends up marrying you, please marry her after she turns 32 because Rahu moves its eclipse after 32 in the second house if it is in enemy sign (we don't know here).
This is my understanding but since no signs or nakshatra are here, so please do not get upset with this analysis. Bottomline is this, Rahu is a obsessive, negative energy which wants more and more and more AND this is how it effects the house it is sitting.