Contractual Purity: Since she was a Teen Idol, this was inevitable. For instance, while she did engage in relationships during her Blümchen-tenure, they only came to light long afterwards. She also had a general "virginal" image to appeal to young girls, which is reflected in her first ballad "Gib mir noch Zeit"/"Give Me More Time" (which is about sexual abstinence).
Averted with Jasmin herself; she mostly looks back fondly on her Blümchen-career. The reason it took her so long to make a comeback had more to do with the fact that she was getting older, combined with simply wanting to be free to make her own career-related choices (something that was a lot harder during her original Blümchen days). Eventually she ended up changing her mind due to the 90s nostalgia boom, combined with the fact that nowadays she has more control over her own image anyway.
Seems to be played more straight with one of her former producers, Stani "Silence" Djukanovic. When Jasmin announced her comeback as Blümchen in 2019, he responded along the lines of "I have nothing to do with this, what's in the past should stay in the past".
Non-Singing Voice: Most likely the case for the original Blümchen era. It should be noted that this was a common practice at the time in Europe; many similar acts (such as, indeed, Milli Vanilli most infamously) partook in this (however, unlike Milli Vanilli, nowhere on any Blümchen album liner notes did they credit the "wrong" singer; instead, the lead singer's name isn't mentioned at all). For those curious, the actual singing voice at the time was most likely provided by House Music vocalist Alexandra Prince, who has also been associated with other projects of the era (e.g. Sqeezer, Nana, Laava, etc.). Alex herself claims she was only a backup singer (and she was credited as such on the fourth Blümchen album), and the original Blümchen producers claim that Jasmin's voice was "pitched to hell and back", but these claims are likely untrue, especially after Alexandra Prince-collaborator Melbeatz pretty much confirmed it in an interview (video in German).
Averted with the songs Jasmin has released under her real name, as well as the newer Blümchen releases (since this practice has fallen out of favor in recent years). It should also be noted that the spoken bits on the original Blümchen songs were always done by Jasmin herself (except perhaps on the first album). She also sometimes sang live during the original Blümchen era (albeit over the original track), showing that she does in fact have talent.
Similarly Named Works: Somehow, Jasmin managed to do this to herself. As Blümchen, she had recorded a song called "Schmetterlinge"translationlit. "Butterflies", which is also the name of the English version for her second album. Whereas one of her unreleased leaked songs for her scrapped debut that was going to be released under her real name was called "Schmetterling"translationlit. "Butterfly", as in singular.
Her German The Bangles cover "Gehn wie ein Ägypter" ("Walk Like an Egyptian") was originally planned to be released as a single; in fact, a radio mix as well as an extended mix were already finished, but the single got cancelled. Instead, those mixes were included on the compilation album ''Für immer und ewig", when Jasmin decided to retire the Blümchen-moniker (at least for the time being). Instead, the Jasmin-penned ballad "Ich vermisse dich"translationlit. "I miss you" was released as her "goodbye" single.
She almost released her first album under her real name back in 2004, but it sadly got cancelled. She performed some of the songs live, and a few got leaked on the internet. There were even a few preceding singles. The song "Sonne in Mir" from this era later popped up on the album Von Herzen in updated form.
In 2010, there was a "charts battle" going on to "kick the winner of Deutschland sucht den Superstarnote the German version of Pop Idol; lit. "Germany seeks a super star" off the Christmas Number One spot" by buying copies of the Blümchen single "Boomerang", akin to what was tried in the past with Rage Against the Machine's "Killing In The Name". While this campaign was technically unsuccessful with its goal, it did bring renewed attention to Blümchen's music (even leading to a re-release of her Best OfGreatest Hits Album) before Jasmin herself decided to make her own voluntary comeback nine years later.
The second English Blossom album, In Love..., had several of its tracks remixed in a more poppy, Ace of Base-esque style for the Asian market. This release is widely sought after by fans.
(video in German).